#14309: fix(ui): resolve chat event session key mismatch

## Summary - Fix session key comparison in `handleChatEvent` to handle agent-scoped keys (`agent:<agentId>:<baseKey>`) - Add optimistic rendering of the final assistant message instead of waiting for `loadChatHistory` round-trip ## Problem Chat events from the gateway use agent-scoped session keys (e.g. `agent:main:<key>`), but the UI stores just the base key. The strict `===` comparison caused **all** chat delta and final events to be silently dropped, making the chat appear unresponsive until manual page refresh. ## Changes - Added `sessionKeyMatches()` helper that compares session keys accounting for the `agent:` prefix - Added optimistic append of the final assistant message to `chatMessages` on the "final" event ## Test plan - Verified in Docker-based OpenClaw deployment where gateway token is used as session key - Confirmed streaming deltas now display in real-time - Confirmed final message appears instantly without page refresh Fixes #10132 <!-- greptile_comment --> <h2>Greptile Overview</h2> <h3>Greptile Summary</h3> Fixes a session key mismatch bug where chat events from the gateway using agent-scoped keys (`agent:<agentId>:<baseKey>`) were silently dropped because the UI stores only the base key. Adds a `sessionKeyMatches()` helper for flexible comparison and optimistically appends the final assistant message to avoid waiting for the `loadChatHistory` round-trip. - **Session key matching**: New `sessionKeyMatches` function correctly handles both directions (event key or state key being agent-scoped). The colon-prefixed `endsWith` check prevents false partial matches. - **Optimistic message append**: The final assistant message is appended immediately on the "final" event, then `loadChatHistory` replaces the entire array with authoritative server data. There's a brief window where a duplicate could flash on slow connections, but it's transient. - **Missing test coverage**: The existing test file (`chat.test.ts`) doesn't cover agent-scoped key matching or the optimistic append behavior. <h3>Confidence Score: 4/5</h3> - This PR is safe to merge with low risk — it fixes a real bug that made chat appear unresponsive. - The session key matching logic is sound, and the optimistic append is a reasonable UX improvement backed by `loadChatHistory` replacing the full array. Minor concerns: potential brief duplicate flash and missing test coverage for the new behavior. - No files require special attention, though `ui/src/ui/controllers/chat.test.ts` should be updated with new test cases. <!-- greptile_other_comments_section --> _{(2/5) Greptile learns from your feedback when you react with thumbs up/down!} <!-- /greptile_comment -->