feat(app): live session update + tool renderer + input_tokens migration

SessionDetail live update:
- Extract session-view-state.mjs: capture scroll position, disclosure
  (open/skill-md-open) state, and visible-UUID anchor before refresh;
  reconcile messages by UUID (in-place update, append tail only); restore
  scroll and disclosure state after DOM patch. findLastMessageAtOrAbove uses
  binary search (O(log n)) instead of linear scan.
- scrollRevision tracks user scrolls during refresh to avoid stale anchors
  overriding manual navigation.
- Throttle onScroll to one rAF per frame.

Tool renderer:
- Extract tool-renderer.js: standalone module for rendering tool call cards
  (Read/Write/Edit diffs, Bash terminal output, search results, JS/TS
  syntax highlighting). Replaces inline rendering in SessionDetail.
- tests/app-tool-renderer.test.mjs covers escaping, highlighting, and
  terminal formatting.

Input tokens semantics migration:
- Claude provider now sums input_tokens + cache_creation_input_tokens +
  cache_read_input_tokens into a single input_tokens value (was previously
  only the raw field, undercounting when cache tokens are present).
- One-time index-wide re-parse triggered when the marker
  __claude_input_tokens_include_cache_v1__ is absent and the DB already
  has token data (self-healing on first build after upgrade).
- App indexer.ts carries the same marker check for the app's build path.

Also:
- PRODUCT.md: product register (users, purpose, brand, design principles,
  accessibility targets).
- README.md: minor wording updates.

Co-Authored-By: Codex (GPT-5) <noreply@openai.com>

tests/persist.test.mjs

@@ -22,7 +22,7 @@ function fixtureUnit() {
   const lines = [
     { type: 'ai-title', aiTitle: 'Persist Session' },
     { uuid: 'u1', type: 'user', timestamp: '2026-06-10T10:00:00Z', cwd: '/proj', message: { role: 'user', content: 'hi' } },
-    { uuid: 'a1', type: 'assistant', timestamp: '2026-06-10T10:00:05Z', message: { role: 'assistant', model: 'm', content: [{ type: 'tool_use', id: 'tc1', name: 'Read', input: { file_path: '/f' } }] } },
+    { uuid: 'a1', type: 'assistant', timestamp: '2026-06-10T10:00:05Z', message: { role: 'assistant', model: 'm', content: [{ type: 'tool_use', id: 'tc1', name: 'Read', input: { file_path: '/f' } }], usage: { input_tokens: 10, output_tokens: 5, cache_creation_input_tokens: 20, cache_read_input_tokens: 30 } } },
     { type: 'system', subtype: 'turn_duration', parentUuid: 'a1', durationMs: 999 },
     { uuid: 'u2', type: 'user', timestamp: '2026-06-10T10:00:10Z', message: { role: 'user', content: [{ type: 'tool_result', tool_use_id: 'tc1', content: 'body', is_error: false }] } },
     { type: 'system', subtype: 'away_summary', uuid: 's1', timestamp: '2026-06-10T10:00:11Z', content: 'sum' },
@@ -56,6 +56,9 @@ test('persist writes all record kinds from one claude parse', () => {
 
   // turn_duration applied via targeted UPDATE.
   assert.equal(db.prepare('SELECT turn_duration_ms FROM messages WHERE uuid=?').get('a1').turn_duration_ms, 999);
+  const usage = db.prepare('SELECT input_tokens, output_tokens FROM messages WHERE uuid=?').get('a1');
+  assert.equal(usage.input_tokens, 60);
+  assert.equal(usage.output_tokens, 5);
 
   // Cursor persisted into index_state (mtime:lines → two columns).
   const state = db.prepare('SELECT lines_processed FROM index_state WHERE jsonl_path=?').get(unit.key);