fix: address PR #1641 review comments (round 3)

- Fix migration version conflict: addSessionPlatformSourceColumn now uses v25
- Sanitize observation titles in file-context deny reason (strip newlines, limit length)
- Guard json_each() with LIKE '[%' check for legacy bare-path rows
- Guard /stream SSE endpoint with 503 before DB initialization
- Scope bun-runner signal exit handling to start subcommand only
- Normalize platformSource at route boundary in DataRoutes

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

src/cli/handlers/file-context.ts

@@ -150,7 +150,7 @@ function formatFileTimeline(observations: ObservationRow[], filePath: string): s
     const chronological = [...dayObservations].sort((a, b) => a.created_at_epoch - b.created_at_epoch);
     lines.push(`### ${day}`);
     for (const obs of chronological) {
-      const title = obs.title || 'Untitled';
+      const title = (obs.title || 'Untitled').replace(/[\r\n\t]/g, ' ').slice(0, 120);
       const icon = TYPE_ICONS[obs.type] || '\u2753';
       const time = compactTime(formatTime(obs.created_at_epoch));
       lines.push(`${obs.id} ${time} ${icon} ${title}`);