feat: refine notes workspace and add canvas zoom

Simplify sidebar selection and note record framing, compact the empty composer, and emphasize note titles. Replace redundant AI comment headings with an accessible panel toggle.

Add view-only canvas zoom and fit width, correct PDF import/export icons, and allow image files up to 20 MiB. Include regression coverage and updated design documentation.

Release note: Notes have clearer navigation and a more compact writing area. Canvases support zoom and fit width, and image imports accept files up to 20 MiB.

docs/features/magic-notes/progress.md

@@ -1,5 +1,22 @@
 # Magic Notes Progress
 
+## 2026-09-19: Canvas Image Import Size
+
+- Raised the canvas image file limit to 20 MiB inclusive and updated its error
+  message and derived restoration bound. The authoritative limit is in the
+  [canvas integration reference](../../../src/renderer/src/magic-canvas/README.md#editor-limits).
+- Real Electron exercised File input, FileReader, Fabric insertion, flush, model
+  conversion and remount: 2 MiB + 1 byte and exactly 20 MiB were retained;
+  20 MiB + 1 byte was rejected with the updated message. Fixtures use a valid
+  one-pixel PNG padded to each byte boundary, not a large decoded pixel image.
+- Production preload/registered IPC handlers with mocked Electron transport and
+  real SQLite/files passed 20 MiB create, update and database reopen checks.
+  Shared canvas validation and file persistence impose no smaller byte budget.
+  Rich-text attachment budgets and the PDF import limit are unchanged.
+- Validation: `npx vitest run tests/canvas-core.electron.test.ts src/main/magic-notes/canvas-ipc.integration.test.ts src/main/magic-notes/magic-note-storage.test.ts src/main/magic-notes/rich-content.test.ts src/renderer/src/magic-canvas`
+  passed 66 tests in 8 files. `npm run typecheck` and `npm run lint` passed.
+  The full suite and a combined native Electron IPC save scenario were not run.
+
 ## 2026-09-19: Resizable Record Index
 
 - The record index defaults to 168px and supports pointer resizing from its right
@@ -359,7 +376,8 @@
 
 - The shared canvas viewport explicitly handles horizontal and vertical wheel
   input in annotation, flow-text and read-only modes. Shift with vertical-only
-  input scrolls horizontally. Ctrl input is left to the existing browser path.
+  input scrolls horizontally. Ctrl input was initially left to the browser;
+  the View Zoom update below assigns Ctrl/Command + wheel to canvas zoom.
   Default scrolling is prevented only when the viewport actually moves; page
   scrolling remains available at boundaries or without canvas overflow.
 - Removed scroll-chain containment. The Electron baseline reproduced boundary
@@ -370,6 +388,36 @@
 - Typecheck and lint passed. The full test run during this fix reported 4,682
   passed, 67 skipped and one unrelated Agent package inventory timeout.
 
+## 2026-09-19: Canvas View Zoom
+
+- Implemented editor/read-only zoom using the shared core. Controls and view-only
+  invariants are documented in the
+  [canvas reference](../../../src/renderer/src/magic-canvas/README.md#view-zoom)
+  and root UI design. The persisted model and export dimensions are unchanged.
+- Real PDF plus flow validation reproduced an existing cleared-background defect:
+  automatic pagination reassigned an unchanged canvas width/height, erasing its
+  bitmap. Layout now retains the bitmap when dimensions are unchanged.
+- Focused validation passed 9 files / 140 tests: `canvas-wheel`, `canvas-flow`,
+  `canvas-note`, canvas `model`, `MagicCanvasEditor`, `MagicCanvasThumbnail`,
+  `MagicNoteContent`, `MagicNotesWorkspace`, and `tests/canvas-core.electron.test.ts`.
+- `node tests/magic-canvas-wheel.electron.mjs`: 41 checks passed in Electron 43.2.0.
+  Native input covered pen coordinates and object move/scale at 50% and 200%,
+  second-page Quill click/typing, Ctrl wheel, ordinary/Shift/diagonal wheel and
+  boundary propagation. Real PDF background pixels, unchanged PNG captures and
+  794-by-1123 output dimensions, stable flow pagination, zero view-only changes,
+  readonly controls, displayed page heights and fit-width resize all passed.
+  Dark narrow layout included a real 560px window resize across the responsive
+  padding breakpoint while the host width remained 360px.
+- `npm run typecheck` and focused ESLint on all six changed JavaScript/test files
+  passed. Final `npm run lint` encountered two `react-hooks/immutability` errors
+  at lines 18/27 of concurrently added `src/renderer/src/FloatingPortal.tsx`;
+  those parallel changes were left intact. `git diff --check` passed.
+- No full test suite, production build, physical-device test or macOS session was
+  run in this change. Meta-wheel is covered by focused tests. The Electron fixture
+  uses production canvas modules/styles with real Fabric, Quill and PDF.js; it
+  does not claim complete App-shell or release-package validation. No model calls
+  or commits were made. Deployed Agent paths are unaffected.
+
 ## 2026-09-19: Single Navigation Button and Unframed Note Detail
 
 - Replaced the two header tabs with one destination-labelled button and icon,