Bundles 2 PRs:
- #1366 fix: guard finalizeThinkingCard with session ID check (with pre-release fix)
- #1367 fix(clarify-sse): stale-detector health timer (Opus SHOULD-FIX from v0.50.249)
Pre-release fix on #1366: the contributor's guard depends on
liveAssistantTurn.dataset.sessionId, but no code in the repo sets
that attribute. Without the fix, the guard would always early-return
(undefined !== sid is always true), breaking the streaming UI
completely — every assistant turn's thinking card would stay open
forever. Added per-site stamps at all 3 places that create
liveAssistantTurn in static/ui.js, plus a regression test that fails
any future creation site that forgets the stamp.
