feat: add file-backed canvas notes

Magic Notes previously supported rich-text records without a paged drawing or
PDF annotation workflow. Add the integrated PeopleLib Fabric and Quill editor
with flowing text, pen/highlighter, object transforms, images, paper templates,
PDF backgrounds with native text extraction, and raster PDF export. Saves are
manual; undo/redo remains scoped to an annotation page or Quill mode.

Analyze drafts, saved canvases and canvas-source todos with page images and
text when the default model supports images, or an explicitly labelled
text-only fallback. Keep successful saves when automatic analysis fails and
prevent MCP plain-text replacement of canvas records.

Move entry bodies and binary assets into local note files with schema 38
migration and verified readback. SQLite retains metadata, indexes, revisions,
todos and comments. Backups must coordinate SQLite and the adjacent notes
directory while writes are paused or the app is closed; no one-click backup
action is included.

Show a continuous record stream with independent collapsible record index and
AI pane, real first-page thumbnails, and scroll-only record navigation. Open a
blank text/canvas composer by default and reset it after creation. Protect
unsaved drafts and establish normalized editor baselines after saving so clean
records do not prompt again when leaving.

Validation: latest recorded focused run passed 149 tests across five files;
typecheck, lint and git diff --check passed. The prior user-reported full run
passed 4,713 tests before later corrections and UI changes; it is not a full
validation of this final snapshot. Tests were not rerun for this commit, as
requested; independent systematic review follows the commit.

Release note: Create paged notes with handwriting, flowing text and PDF
annotations, browse records through thumbnails, and request AI comments with
an explicit text-only fallback. Existing notes migrate to local file storage;
backups now need both the database and notes directory.

src/shared/magic-notes-contracts.ts

@@ -246,6 +246,42 @@ export type MagicNoteRichContent = z.infer<
   typeof magicNoteRichContentSchema
 >
 
+const canvasDataUrlSchema = embeddedDataUrlSchema(Number.MAX_SAFE_INTEGER)
+export const magicNoteCanvasContentSchema = z.object({
+  version: z.literal(2),
+  kind: z.literal('paged-canvas'),
+  pages: z.array(z.object({
+    id: z.string().min(1),
+    width: z.number().finite().positive().max(3000),
+    height: z.number().finite().positive().max(3000),
+    background: z.union([
+      z.object({ type: z.literal('template'), template: z.enum(['blank', 'ruled', 'grid', 'dot']) }).strict(),
+      z.object({ type: z.literal('pdf'), assetId: z.string().min(1), pageNumber: z.number().int().positive(), text: z.string().optional() }).strict()
+    ]),
+    objects: z.array(z.record(z.string(), z.unknown())),
+    flowAuto: z.boolean().optional()
+  }).strict()).min(1).max(50),
+  flow: z.object({ version: z.literal(1).optional(), ops: z.array(z.object({
+    insert: z.union([z.string(), z.record(z.string(), z.unknown())]),
+    attributes: z.record(z.string(), z.unknown()).optional()
+  }).strict()).max(5000) }).strict().superRefine((flow, context) => {
+    const length = flow.ops.reduce((total, op) => total + (typeof op.insert === 'string' ? op.insert.length : 0), 0)
+    const last = flow.ops.at(-1)?.insert
+    const terminalNewline = typeof last === 'string' && last.endsWith('\n') ? 1 : 0
+    if (length - terminalNewline > 20_000) context.addIssue({ code: 'custom', message: '画布正文不能超过 20,000 字符（不含末尾换行）', path: ['ops'] })
+  }).optional(),
+  assets: z.array(z.object({
+    id: z.string().min(1), name: embeddedFileNameSchema,
+    mimeType: embeddedMimeTypeSchema, dataUrl: canvasDataUrlSchema
+  }).strict()),
+  preview: z.string().optional()
+}).strict()
+
+export type MagicNoteCanvasContent = z.infer<typeof magicNoteCanvasContentSchema>
+export const magicNoteContentSchema = z.union([magicNoteRichContentSchema, magicNoteCanvasContentSchema])
+export type MagicNoteContent = z.infer<typeof magicNoteContentSchema>
+export type MagicNoteAnalysisInputMode = 'text' | 'images' | 'canvas-images' | 'text-fallback'
+
 export const magicNoteCreateSchema = z
   .object({
     title: z.string().trim().min(1).max(100)
@@ -275,7 +311,7 @@ export const magicNoteDeleteSchema = z
 export const magicNoteEntryCreateSchema = z
   .object({
     noteId: magicNoteIdSchema,
-    content: magicNoteRichContentSchema
+    content: magicNoteContentSchema
   })
   .strict()
 export type MagicNoteEntryCreateInput = z.infer<
@@ -285,7 +321,7 @@ export type MagicNoteEntryCreateInput = z.infer<
 export const magicNoteEntryUpdateSchema = z
   .object({
     entryId: magicNoteIdSchema,
-    content: magicNoteRichContentSchema,
+    content: magicNoteContentSchema,
     expectedRevision: z.number().int().nonnegative()
   })
   .strict()
@@ -323,7 +359,8 @@ export const magicNoteAnalysisOptionsSchema = z
   .object({
     requestId: z.string().uuid(),
     direction: magicNoteCommentDirectionSchema,
-    format: magicNoteCommentFormatSchema
+    format: magicNoteCommentFormatSchema,
+    canvasImages: z.array(z.object({ pageId: z.string().min(1), dataUrl: z.string().regex(/^data:image\/(?:jpeg|png);base64,[A-Za-z0-9+/]+={0,2}$/) }).strict()).max(50).optional()
   })
   .strict()
 export type MagicNoteAnalysisOptions = z.infer<
@@ -339,7 +376,7 @@ export const magicNoteAnalyzeSchema = z
 
 export const magicNoteDraftAnalyzeSchema = z
   .object({
-    content: magicNoteRichContentSchema,
+    content: magicNoteContentSchema,
     ...magicNoteAnalysisOptionsSchema.shape
   })
   .strict()
@@ -375,6 +412,7 @@ export type MagicNoteComment = {
   direction?: MagicNoteCommentDirection
   format?: MagicNoteCommentFormat
   analyzedAt?: string
+  inputMode?: MagicNoteAnalysisInputMode
 }
 
 export type MagicNoteAnalysisStreamEvent = {
@@ -388,7 +426,7 @@ export type MagicNoteAnalysisStreamEvent = {
 export type MagicNoteEntry = {
   id: string
   noteId: string
-  content: MagicNoteRichContent
+  content: MagicNoteContent
   plainText: string
   comments: MagicNoteComment[]
   analyzedAt?: string
@@ -412,6 +450,10 @@ export type MagicNoteDetail = MagicNoteSummary & {
   entries: MagicNoteEntry[]
 }
 
+export type MagicNoteEntryCreateResult = MagicNoteDetail & {
+  createdEntryId: string
+}
+
 export type MagicNotesSnapshot = {
   notes: MagicNoteSummary[]
 }
@@ -450,6 +492,7 @@ export type MagicNoteDraftAnalysis = {
   id: string
   comments: MagicNoteComment[]
   analyzedAt: string
+  inputMode?: MagicNoteAnalysisInputMode
 }
 
 export type MagicNoteSearchResult = {