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• childExists only checks local session-list cache, not whether the child sync succeeded.
• If the child is stale in sync.data.session but session.get now returns 404, sync fails and is swallowed, yet childExists() can remain true, so clicking can still navigate to a missing child session.
• The added test only proves that a synthetic rejected promise with .catch(() => {}) does not emit unhandledRejection. It does not mount Task, call sync.session.sync, verify stale rendering, or verify navigation behavior.
• It also catches all errors and still leaves a clickable affordance via an always-present onClick.

Thanks for the thorough review @kommander — all feedback addressed in this push.

Changes:

1. Replaced childExists memo with sessionMissing signal — The old memo checked sync.data.session (stale cache populated by bootstrap/SSE, not by sync outcome). The new signal tracks the actual sync failure: createSignal(false) → setSessionMissing(true) in .catch(). Single source of truth based on what actually happened.

2. Error is recorded, not swallowed — .catch() now sets the signal instead of being a no-op catch(() => {}). The error state propagates to the UI layer.

3. onClick conditionally passed — When sessionMissing() is true, onClick is undefined. InlineTool already handles this: no hover state, no click affordance, muted text. No more "clickable but does nothing" state.

4. Removed the synthetic test — Agreed it was testing JavaScript, not our code. No TUI testing infrastructure exists in this codebase, so no test is better than a misleading one.

Net diff: +12 -34 lines
Typecheck: All 14 packages pass clean

Resolved merge conflicts with upstream/dev. The fix now incorporates the new retry error dialog feature:

• sessionMissing signal tracks actual sync failure (not stale cache)
• onClick is conditionally passed (no affordance when session missing)
• Preserved the retry error dialog from upstream
• Net change: +17 -18 lines