fix(desktop): route forum message links to the post, not the post list - #7361

Return the navigation result before acknowledging the link

When an OS message link arrives while a thread reply is being edited, the registered navigation guard makes goChannel or goForumPost resolve to false, but useOpenMessageLink discards that result and this callback unconditionally returns true. listenForNavigationDeepLinks consequently removes the durable queue entry even though navigation was refused, so finishing or cancelling the edit cannot retry the link. Propagate the navigation helper's acceptance result instead of always acknowledging it.

AGENTS.md reference: AGENTS.md:L167-L174

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Cancel link resolution when its community unmounts

If getEventById remains pending while the user switches communities, the effect cleanup only sets cancelled before this promise continuation runs; the old callback can therefore call the global router after the new community is active and navigate it to the previous community's channel or post. The deep-link drain generation prevents acknowledgement but does not prevent this stale route write, so pass a lifecycle signal into this path and recheck it after destination resolution before navigating.

AGENTS.md reference: AGENTS.md:L176-L186

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Exercise the production routing seam in the regression test

These tests import only the pure destination resolver and never exercise useOpenMessageLink or either production entry point. Replacing the new hook's branch with an unconditional goChannel call would therefore leave every test green while recreating #7315, so add a navigation-seam test that asserts forum links actually invoke goForumPost and stream links invoke goChannel.

AGENTS.md reference: AGENTS.md:L188-L192

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Keep failed destination lookups queued

When get_event fails transiently or the target was deleted, this catch converts the failure into a channel destination. For a queued OS link to a forum message, goChannel can then return success, causing drainPendingNavigationDeepLinks to acknowledge and remove the durable entry even though the forum post was never opened. Propagate a failed resolution to the queue consumer so it remains retryable; any best-effort in-app fallback can be handled separately.

AGENTS.md reference: AGENTS.md:L167-L174

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Fixed in e775087. Failed event lookups and forum comments without a resolvable root now return an unresolved destination. The OS deep-link caller disables channel fallback, so these cases neither navigate nor acknowledge the durable entry. In-app clicks retain their best-effort channel fallback.

Production-hook/drain regressions cover transient errors, missing events, successful retry, and missing forum roots. Re-enabling fallback for the queue consumer fails 3 tests. Focused tests pass 32/32; the final pre-push desktop suite, typecheck, lint and file-size gates passed.

Fence overlapping message-link resolutions

When a user activates two message links before the first get_event request completes—for example, two links within the currently mounted channel—the faster second lookup navigates first, but the slower older lookup can later navigate back over it. The current abort checks only cover component teardown or an external signal, not superseding activations, so destination resolution needs a latest-request generation fence before routing.

AGENTS.md reference: AGENTS.md:L176-L179

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Fixed in e775087. Each activation replaces a shared request token, checked after destination resolution and before routing or fallback. This also fences competing activations from separate mounted Markdown renderers. resetCommunityState invalidates the token before asynchronous teardown.

Production-hook tests cover older success/failure arriving after a newer activation, separate hook instances, and community reset before unmount. Removing the request fence fails 4 tests. Focused tests pass 32/32; the final pre-push desktop suite, typecheck, lint and file-size gates passed.

Verify the event belongs to the linked channel

For a malformed or manually authored link whose channel names A while id names a forum event in B, this unscoped lookup routes to /channels/A/posts/<B-event>. The forum thread backend fetches its root by exact ID without an #h filter and assigns the supplied channel ID, so the UI can display B's post under A and a reply can then be submitted into A against that foreign root. Compare the fetched event's h tag with channelId before returning any destination, as the existing message-link metadata resolver already does.

AGENTS.md reference: AGENTS.md:L265-L267

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Let terminal lookup failures advance the deep-link queue

When get_event returns the definitive event not found response for a deleted message, this catch treats it like a retryable outage and the OS caller returns false. Because take_pending_navigation_deep_link repeatedly returns the unchanged front of its VecDeque and the drain stops before acknowledging it, every later valid channel or message link is blocked until the queue is cleared by a community switch or process exit. Fresh evidence beyond the earlier retry-retention discussion is this FIFO head-of-line blocking for permanent failures; distinguish terminal not-found errors so the drain can resolve or discard that item and continue.

AGENTS.md reference: AGENTS.md:L198-L201

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