Native format: document.save can write path coordinates at a fixed precision

Native files store every anchor and handle as a full double, such as
3.4876474632797176, so a file of traced art is larger than it needs
to be.

document.save, file.saveAs, file.saveCopy and file.saveAsTemplate take
precision (0 to 9) for native files. The save rounds the anchors and
handles of path objects, Live Corners' uncut outlines, blend spines,
envelope outlines, Intertwine areas and brush art to that many decimal
places, in the layers, symbols, graph designs, patterns and opacity
masks, and in the art that placed documents become in files for older
versions. Colors, transforms, opacity and type are written exactly.
Without precision the file is written as before, and Save does not
remember the option. A .ai file, saved or exported, ignores precision.
The VectorCraft Options dialog shows no row for it.

A save given precision beside the path for a format that does not read
it (SVG, PDF, .ai and .ait) says so in its warnings, as it does for
compress, version and preview. MCP save_file passes precision on to the
save as it passes the other native options, and its schema, description
and docs/mcp.md list it.

docs/mcp.md

@@ -420,7 +420,7 @@ objects' fills or strokes differ (`fillMixed` / `strokeMixed`, drawn as a "?" pr
 | `open_panel` | `{panel}` | Remote only. `panel` is a panel id (`layers`, `swatches`, `colorGuide`, …, as `window.panel` takes) or its display label (`"Color Guide"`), in any case. |
 | `screenshot` | `{path?, scale?, artboard?, window?, max_side?}` | Returns MCP image content (`image/png`, base64) plus a text block. Renders the artboard with the pixels of a PNG `export` with `background: "white"` at the same scale; `window:true` captures the app window (remote only), as `ui_screenshot` does, and `max_side` (1–4096, window captures only) scales the returned image down as described for `ui_screenshot`. With `path` the backend (the headless session or the app) writes the PNG there too; a window capture written there keeps its full size with `max_side`. |
 | `open_file` | `{path}` | Opens any readable file as a new active document: `.vectorcraft`/`.drawcraft`, `.vctemplate`, `.svg`/`.svgz`, `.pdf`/`.ai`, `.ait`, `.eps`/`.epsf`, `.ps`, `.dxf`, `.emf`, `.wmf`, PNG, JPEG, GIF, WebP, TIFF, BMP, Targa (`.tga`/`.vda`/`.icb`/`.vst`), PSD/PSB (an image opens as a document of its pixel size; a Photoshop file as its merged image). Templates (`.vctemplate`, `.ait`) open as a new untitled document. PDF, `.ai` and SVG files saved with Preserve Editing reopen as the document they carry. The reply is `document.open`'s: its `warnings` say what didn't come in as it was (an EPS whose PostScript can't be read opens as its preview, and the warning names the PostScript error, the operator and the procedure). `run_command document.formats` lists the formats. |
-| `save_file` | `{path?, compress?, version?, preview?, options?}` | Runs `document.save`: the document's own file in its own format (native `.vectorcraft` unless it was opened from or saved as SVG, PDF or a restorable `.ai`; then `warnings` say what that format loses). A path's extension picks the format (`.vectorcraft`, `.vctemplate`, `.pdf`, `.svg`, `.svgz`, `.ai`: a PDF carrying the native document, which reopens editable). For a native file, `compress: true` gzips it (default: the `useCompression` preference, Preferences › File Handling › Use Compression), `version` (1 to 4) writes it for an older VectorCraft (1 and 2 are never compressed, and `version: 2` with `compress: true` is an error), and `preview: true` embeds a PNG of the first artboard. `options` passes the format's save options as `run_command document.formats` lists them. When `compress`, `version` or `preview` is given both at the top level and in `options` with different values, the call is an error (`` `compress: true` and `options.compress: false` disagree: give the option once ``) and nothing is written. The save drops each option the written format doesn't read. The reply's `warnings` then name each such option given (for example `` `compress` was not used: SVG files don't read it `` for an `.svg` path, and `` `options.preview` was not used: … `` for a key in `options`; a `.ai` file reads `compress` but not `version` or `preview`). `run_command document.save` and the other save commands refuse any option given beside the path and in `options` with different values, and give the same warning for a top-level `compress`, `version` or `preview`. The headless session and the app receive the same `app.save` params, and the app is also sent `wait: true`: the call returns once the file is written, or with the error (such as a path outside the write root), even with Background Save on. When the save asks first (the question before replacing a file that opened with losses, or on macOS and Linux the file dialog for an untitled document without `path`), the reply is `{pending}` or `"cancelled"` as before, and the save that runs after the answer uses the Background Save preference. |
+| `save_file` | `{path?, compress?, version?, preview?, precision?, options?}` | Runs `document.save`: the document's own file in its own format (native `.vectorcraft` unless it was opened from or saved as SVG, PDF or a restorable `.ai`; then `warnings` say what that format loses). A path's extension picks the format (`.vectorcraft`, `.vctemplate`, `.pdf`, `.svg`, `.svgz`, `.ai`: a PDF carrying the native document, which reopens editable). For a native file, `compress: true` gzips it (default: the `useCompression` preference, Preferences › File Handling › Use Compression), `version` (1 to 4) writes it for an older VectorCraft (1 and 2 are never compressed, and `version: 2` with `compress: true` is an error), `preview: true` embeds a PNG of the first artboard, and `precision` (0 to 9) rounds path anchors and handles to that many decimal places for that save only (colors, transforms and type stay exact). `options` passes the format's save options as `run_command document.formats` lists them. When `compress`, `version`, `preview` or `precision` is given both at the top level and in `options` with different values, the call is an error (`` `compress: true` and `options.compress: false` disagree: give the option once ``) and nothing is written. The save drops each option the written format doesn't read. The reply's `warnings` then name each such option given (for example `` `compress` was not used: SVG files don't read it `` for an `.svg` path, and `` `options.preview` was not used: … `` for a key in `options`; a `.ai` file reads `compress` but not `version`, `preview` or `precision`). `run_command document.save` and the other save commands refuse any option given beside the path and in `options` with different values, and give the same warning for a top-level `compress`, `version`, `preview` or `precision`. The headless session and the app receive the same `app.save` params, and the app is also sent `wait: true`: the call returns once the file is written, or with the error (such as a path outside the write root), even with Background Save on. When the save asks first (the question before replacing a file that opened with losses, or on macOS and Linux the file dialog for an untitled document without `path`), the reply is `{pending}` or `"cancelled"` as before, and the save that runs after the answer uses the Background Save preference. |
 | `export` | `{path?, format?, scale?, artboard?, range?, selection?, outlineText?, options?}` | `svg`, `svgz`, `pdf`, `ai` (the PDF-compatible `.ai` that Save writes, which carries the document when every artboard is written in order), `eps`, `dxf`, `emf`, `wmf`, `png`, `jpg`, `webp`, `gif`, `png8` (an indexed `.png`), `tiff`, `bmp`, `tga`, `psd` (layered), `txt` (the document's text), `vectorcraft` or `template` (a native template). The tool's `format` enum and `document.formats` list them, generated from the engine's format table. When `format` is omitted, it comes from the path's extension. PDF and `.ai` write one page per artboard: all of them, or `artboard` (0-based) / `range` (`"1-3, 5"`, 1-based). SVG, SVGZ and EPS write one file per chosen artboard. Rasters, DXF, EMF and WMF write one artboard, or one file per chosen artboard with `options: {"useArtboards": true}`. Rasters also take `options: {"rect": [x, y, width, height]}` (page points, y down): that area of the page at the given `ppi`/`scale`, without an artboard and without changing the document; it is refused with `artboard`, `range` or `useArtboards`, with a non-positive or non-finite size, and for non-raster formats. `options` carries more format options (e.g. `{"quality": 80}` for JPEG). `selection: true` exports the selected objects cropped to their bounds (the reply adds their `bounds`, and reports `format` and the encoder's `warnings` as a whole-document export does); `outlineText: true` writes SVG text as paths. Template layers are left out, live effects are kept, and exporting `vectorcraft` never changes the document's path. Without `path` the bytes come back as `dataBase64`. Both backends run the same `document.export` call. |
 | `add_text` | `{text, x?, y?, width?, height?, fit?, fitMinPercent?, path?, mode?, pathEffect?, size?, font?, color?, justify?, vertical?}` | Point type at (x, y) (`justify`: `left`, `center` or `right` starts, centres or ends each line on x); area type with `width`/`height` (`fit`: `none`, `autoHeight`, `shrinkText`, as `text.areaOptions`); or `path` + `mode` (`area`/`onPath`) to flow text in or along a path, with `pathEffect` (`rainbow`, `skew`, `3dRibbon`, `stairStep`, `gravity`); `justify` (also `auto`, `justifyAll`) aligns the paragraphs of every kind, as `text.setStyle` does later. `vertical: true` uses the existing vertical writing mode for every kind (default `false`, horizontal). Returns `{id}`, with `overflow: true` when the text doesn't fit its frame or path. |
 | `apply_effect` | `{effect?, params?, ids?}` | Appends a live effect. Without `effect`, returns the effect catalogue with parameters and defaults. |
@@ -596,7 +596,11 @@ can't be read becomes a placeholder in its box, named in `warnings` and `missing
 Native files: `run_command document.save {compress: true}` writes a gzip-compressed `.vectorcraft` (the
 `useCompression` preference makes that the default for saves; compressed files open like any other, told apart by
 their content). `version: 2` or `1` writes a file older VectorCraft versions open (format name `drawcraft`, never
-compressed), and `preview: true` embeds a PNG of the first artboard, at most 256 px on its longer side. A save writes
+compressed), and `preview: true` embeds a PNG of the first artboard, at most 256 px on its longer side.
+`precision: 4` (0 to 9) rounds the anchors and handles of paths to that many decimal places (in the layers, symbols,
+graph designs, patterns, opacity masks and brushes); colors, transforms, opacity and type are written exactly.
+Without `precision` a save writes the coordinates exactly, and Save does not remember it. A `.ai` file ignores
+`precision`. A save writes
 a temporary file and renames it over the old one, so a failed save never damages the file; only the images the
 document uses are written, and document keys written by a newer version are kept.
 An uncompressed file is indented JSON when the document has at most 2,000 layers and objects and the indented