Phase 7: browser-side spell check (nspell, en-US)

Vendored Hunspell en.aff/en.dic into web/public/dictionaries/en/ (served as a
static asset + embedded in the binary, kept out of the JS bundle). dictionary-en
moved to a devDep — only used to source the files.

- useSpellChecker (App-level, loads once/session): fetches the dict, builds an
  nspell instance, replays a localStorage personal word list; addWord persists
  and bumps a version so consumers re-decorate. Ambient types in
  src/types/nspell.d.ts (the package ships none).
- SpellCheck Tiptap extension: misspellings as ProseMirror decorations (no
  stored marks), recomputed on edit / caret move / checker swap. Latin-only
  tokenizer so CJK is never flagged; skips short tokens + all-caps acronyms;
  exempts the caret word to avoid mid-typing jitter. Reuses mapOffset (now
  exported from SuggestionHighlight); wordAt resolves the exact span on click.
- MisspellCard: soft rose wavy underline, bilingual popover with up to 5 nspell
  corrections (click to replace) + add-to-dictionary. Closes on outside-pointer,
  edit, or doc switch.

Chinese spell check intentionally omitted — nspell is dictionary-based and
English-only; Chinese typos (homophone 别字) need an LLM, out of v1 scope.

tsc/vite/go build+vet clean; live server serves both dict files; nspell
behavior smoke-tested.

Claude-Session: https://claude.ai/code/session_016Yr6jELuRc7hyzYLccQKZd

web/package-lock.json

@@ -16,6 +16,7 @@
         "@tiptap/react": "^2.11.5",
         "@tiptap/starter-kit": "^2.11.5",
         "lottie-web": "^5.13.0",
+        "nspell": "^2.1.5",
         "react": "^19.1.0",
         "react-dom": "^19.1.0"
       },
@@ -24,6 +25,7 @@
         "@types/react": "^19.1.0",
         "@types/react-dom": "^19.1.0",
         "@vitejs/plugin-react": "^4.3.4",
+        "dictionary-en": "^4.0.0",
         "tailwindcss": "^4.0.0",
         "typescript": "^5.7.3",
         "vite": "^6.1.0"
@@ -2130,6 +2132,17 @@
         "node": ">=8"
       }
     },
+    "node_modules/dictionary-en": {
+      "version": "4.0.0",
+      "resolved": "https://registry.npmjs.org/dictionary-en/-/dictionary-en-4.0.0.tgz",
+      "integrity": "sha512-3NHnE1uq33ZE/CIwaZ6gqxa4BnglHnxeAcTM0GJ7cmtRGcvX9InMK/IqLtYcUMFCUpUNgybH+DzkqdgAo3F1zg==",
+      "dev": true,
+      "license": "(MIT AND BSD)",
+      "funding": {
+        "type": "github",
+        "url": "https://github.com/sponsors/wooorm"
+      }
+    },
     "node_modules/electron-to-chromium": {
       "version": "1.5.379",
       "resolved": "https://registry.npmjs.org/electron-to-chromium/-/electron-to-chromium-1.5.379.tgz",
@@ -2283,6 +2296,29 @@
       "dev": true,
       "license": "ISC"
     },
+    "node_modules/is-buffer": {
+      "version": "2.0.5",
+      "resolved": "https://registry.npmjs.org/is-buffer/-/is-buffer-2.0.5.tgz",
+      "integrity": "sha512-i2R6zNFDwgEHJyQUtJEk0XFi1i0dPFn/oqjK3/vPCcDeJvW5NQ83V8QbicfF1SupOaB0h8ntgBC2YiE7dfyctQ==",
+      "funding": [
+        {
+          "type": "github",
+          "url": "https://github.com/sponsors/feross"
+        },
+        {
+          "type": "patreon",
+          "url": "https://www.patreon.com/feross"
+        },
+        {
+          "type": "consulting",
+          "url": "https://feross.org/support"
+        }
+      ],
+      "license": "MIT",
+      "engines": {
+        "node": ">=4"
+      }
+    },
     "node_modules/jiti": {
       "version": "2.7.0",
       "resolved": "https://registry.npmjs.org/jiti/-/jiti-2.7.0.tgz",
@@ -2701,6 +2737,15 @@
         "node": ">=18"
       }
     },
+    "node_modules/nspell": {
+      "version": "2.1.5",
+      "resolved": "https://registry.npmjs.org/nspell/-/nspell-2.1.5.tgz",
+      "integrity": "sha512-PSStyugKMiD9mHmqI/CR5xXrSIGejUXPlo88FBRq5Og1kO5QwQ5Ilu8D8O5I/SHpoS+mibpw6uKA8rd3vXd2Sg==",
+      "license": "MIT",
+      "dependencies": {
+        "is-buffer": "^2.0.0"
+      }
+    },
     "node_modules/orderedmap": {
       "version": "2.1.1",
       "resolved": "https://registry.npmjs.org/orderedmap/-/orderedmap-2.1.1.tgz",