feat: track log file size to detect actual changes

[gbasin]

Summary

• Replace mtime-based change detection with file size tracking to avoid false activity updates from backup tools/filesystem syncs that touch log files without modifying content
• Add last_known_log_size column to track file sizes in the database
• Add is_codex_exec column as an optimization to skip matching for codex-exec sessions
• Extract timestamps from log entries for accurate activity tracking instead of relying on mtime

Changes

Core Implementation

• logPoller.ts: Use file size comparison instead of mtime to detect actual log growth
• logPollData.ts: Include file size in log entry snapshots
• logMatchGate.ts: Gate re-matching on size changes rather than mtime
• logMatcher.ts: Add extractLastEntryTimestamp() to parse timestamps from log entries
• db.ts: Add schema migrations for last_known_log_size and is_codex_exec columns

Improvements

• logMatchWorkerClient.ts: Refactor worker init error handling to use proper rejection pattern with typed WorkerInitError class
• App.tsx: Auto-add project to filters when session is selected (if filters are active)

Test plan

• All 375 tests passing
• Lint and typecheck passing
• Added comprehensive tests for extractLastEntryTimestamp function
• Manual testing with backup tools that modify mtime without changing content

🤖 Generated with Claude Code