Preferences ▸ Units drive every length the UI shows and reads (M14.5)

[bflatastic]

Fixes a reported bug: changing Preferences ▸ Units (for example General to Millimeters) didn't update the UI; everything stayed in points. Every length the UI shows and reads now follows the units, live.

• M14.5: Preferences ▸ Units drive every length the UI shows and reads.
  • How document units and the preference fit together:
    • General is the open document's units (Document.units, saved with the file).
    • prefs.set {unitsGeneral} changes the open document's units in one undo step (none if unchanged). It is also what file.new starts in without units, and what shows with no document open.
    • Document Setup changes only that document.
    • The Preferences dialog opens with General set to the document's units, so the two never disagree.
    • Stroke and Type stay app-wide preferences.
  • General units now drive:
    • the Transform panel, Properties and Control bar X/Y/W/H (fields widened so "152.753 mm" fits);
    • Info, Align spacing, Tabs, paragraph indents and Pattern Options;
    • rulers (with fractional steps for large units) and the status-bar X/Y;
    • dialog distances: Move, shapes, Offset Path, Simplify, Split Into Grid, Artboard Options, effects, Transform Each, parameter dialogs, Save PDF bleed and marks;
    • New Document and the home-screen presets;
    • canvas readouts: size, move and Measure labels, and the Live Corners radius.
  • Type units drive font size, leading and baseline shift (Character, Properties, Info).
  • Stroke units now also drive the Appearance panel's weight, the Width tool readout and the Magic Wand's weight tolerance.
  • Typed units: a value with a unit ("5 mm", "12 pt") works in every field. Over MCP the new len_param makes offset, simplify tolerance, grid gutter and text size/leading accept them too. Length preferences show and accept units.
  • More units: all ten are choices (Feet & Inches, Meters, Yards and Feet added).
  • One shared formatter and parser: Session::unit / general_unit / type_unit / default_units, Unit::named / key / readout / number, and PrefKind::Length.
  • Crash fix: the length parser no longer panics on text that starts with a multi-byte character (for example "é5").

docs/mcp.md and docs/control-protocol.md describe the units behaviour.

Known limits:

• "Numbers Without Units Are Points" and East Asian type options have no effect yet.
• Spinner arrows step 1 pt in every unit, as the Stroke panel already did.

Checks

Rebased onto 0e31fc9 (#66). cargo xtask ci passes all 7 steps (fmt, clippy, test, assets, brands, layers, wasm): 1,984 tests, 0 failed.

• Nothing dropped:
  • every test name on main still exists (1,961 → 1,981, no existing test changed);
  • command ids, UI_COMMANDS, menu entries and MCP tools are unchanged.
• New tests:
  • headless frames showing mm in Transform, Properties, the Control bar, Info and the Move, Rectangle and Drop Shadow dialogs, plus Preferences and New Document;
  • format/parse round-trips for every unit;
  • Stroke and Type units;
  • undo and a native round-trip;
  • canvas labels.
• Checked in the running app: panels, Move, Preferences, New Document and the drag readout all show mm.

🤖 Generated with Claude Code