Add anonymous telemetry and debounce inline diff syntax highlighting

[tyulyukov]

Summary

• Telemetry Infrastructure: Add PostHog-based anonymous telemetry with event buffering and batching. Identifier sourced from Codex auth → Claude config → generated anonymous ID (persisted).
• Provider Event Tracking: Record analytics events for session lifecycle (started, recovered, stopped) and turn operations (sent, interrupted, rolled back).
• Startup Heartbeat: Log thread/project counts on server boot for baseline telemetry.
• Debounce Syntax Highlighting: Add 150ms debounce to code highlighting in inline diffs to reduce unnecessary re-renders during collapsed state changes.
• Work Row Height Estimation: Implement height estimation accounting for diff preview sizes (header + line heights, capped at 260px) for accurate virtualization in work log timeline.

Testing

• bun run test — AnalyticsService buffer draining, event batching, and startup heartbeat recording
• bun lint — No new linting violations
• bun fmt — Code formatted to spec
• bun typecheck — No type errors
• Manual: Verify syntax highlighting debounces when toggling diff previews (no jank)
• Manual: Verify work row heights render correctly with/without inline diffs expanded
• Manual: Verify telemetry events are batched and sent to PostHog endpoint