#3474: fix(macos): menu bar activity badge not showing during agent work

## Summary Fixes two macOS issues: 1. **Menu bar activity badge** - Wasn't showing during agent work due to missing state update 2. **Chat window crash** - Prevented crash when opening chat window ## Rebased from #1994 Previous PR was closed due to merge conflicts. This is a clean rebase on current main. ## Changes - Fix activity badge state propagation in menu bar - Add nil check for chat window initialization ## Testing - Verified badge appears during agent activity - Confirmed chat window opens without crash <!-- greptile_comment --> <h2>Greptile Overview</h2> <h3>Greptile Summary</h3> This PR updates macOS agent activity/UI state wiring so the menu bar activity badge reflects active agent work, and it adds a defensive path in chat markdown rendering to avoid a crash when `Textual`’s SwiftPM resource bundle isn’t found in packaged app layouts. Key changes are: - `ControlChannel.routeWorkActivity` now listens to `stream == "lifecycle"` events and converts gateway lifecycle signals into `WorkActivityStore.handleJob` state updates, so the badge can transition into and out of “working”. - `AgentEventsWindow` display logic aligns the stream label/tint mapping with the new lifecycle stream name. - `ChatMarkdownRenderer` conditionally uses `StructuredText` only when Textual resources appear available; otherwise it falls back to plain `Text`. <h3>Confidence Score: 3/5</h3> - Reasonably safe to merge, but the new Textual-bundle gating logic may regress markdown rendering in some packaging/configurations. - ControlChannel’s stream/state mapping is small and localized, and aligns with WorkActivityStore’s started-vs-done semantics. The higher risk is in ChatMarkdownRenderer: bundle detection is eager (static), path-based, and relies on DEBUG heuristics, which could cause unnecessary plain-text fallback or fail to prevent the original crash in some build modes. - apps/shared/MoltbotKit/Sources/MoltbotChatUI/ChatMarkdownRenderer.swift <!-- greptile_other_comments_section --> _{(3/5) Reply to the agent's comments like "Can you suggest a fix for this @greptileai?" or ask follow-up questions!} <!-- /greptile_comment -->