fix(canvas): fix the Activity bell's hover card resurfacing, and wedging, after it navigates

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Problem

Two things go wrong with the Activity bell in the channels nav, both every time:

1. Click the bell → you land on the Activity page. Open any notification from there and the Activity hover card pops up over the task you just navigated to.
2. After that click the bell keeps a pressed/active look, and hovering it never opens the card again.

Why: the bell is both a popover trigger and a nav button, and quill's trigger opens the card on click as well. Our handler runs first, then the trigger's own open lands — still inside the same click, before the route changes — so the card records itself as open. The Activity page only hid that (open={!isActivity && activityOpen}) rather than closing it, so it resurfaced on the next navigation.

The pressed-and-dead-hover half has the same root: refusing an open isn't free. Base UI applies the open to its store before handing it to us, so a false we hand back desyncs the trigger — it keeps data-popup-open / data-pressed, and its hover-open path bails on the stale internal state until the trigger remounts. The old !isActivity gate refused opens the same way, so hovering the bell on the Activity page wedged it too.

Changes

Stop refusing opens rather than papering over the effects:

• The trigger's own click-open is prevented outright (event.preventBaseUIHandler()) — the click's one job is to navigate.
• The Activity page renders the bell with no popover wrapped around it, so there are no hover-opens to refuse there. This matches what the sidebar's Activity row already does.
• The open state now lives in the component that only mounts off the Activity page, so it starts closed on every visit. Nothing to mask, nothing left over, and onOpenChange is a plain mirror.

How did you test this?

Diagnosed by probing the trigger's DOM state through the reported flow, which showed data-popup-open/data-pressed stuck on the bell and hover dead afterwards — both reproducible on main.

• Three regression tests in ChannelNav.test.tsx: no card after the bell navigates and you open a notification, hover still opens the card afterwards, and no leftover popover state on the bell. All three fail on main, pass here.
• Full @posthog/ui suite: 283 files / 2409 tests pass, including the existing hover-open, close-on-unhover, and no-card-on-the-Activity-page tests.
• turbo run typecheck --filter=@posthog/ui and biome check on the touched files: clean.

Not driven in the running Electron app — worth a click-through when you pull it.

Automatic notifications

• Publish to changelog?
• Alert Sales and Marketing teams?

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Created with PostHog Code

[trunk-io]

😎 Merged successfully - details.

[github-actions]

React Doctor found no issues in the changed files. 🎉

_{Reviewed by React Doctor for commit 9926f2e.}

[greptile-apps]

_{Reviews (1): Last reviewed commit: "refactor(canvas): drop comments from the..." | Re-trigger Greptile}

[github-actions]

Contained UI-only fix to a canvas nav popover's open-state handling, with new regression tests covering the exact bug; no risky territory (no auth, billing, API, deps, or CI changes) touched.

• Author wrote 0% of the modified lines and has 12 merged PRs in these paths (familiarity MODERATE).
• 👍 on the PR from greptile-apps[bot].

Gate mechanics and policy version

Gate		Result
prerequisites	✓	all clear
deny-list	✓	no deny categories matched
size	✓	93L, 1F substantive, 132L/2F incl. docs/generated/snapshots — within ceiling
tier	✓	T1-agent / T1c-medium (132L, 2F, single-area, fix)
stamphog 2.0.0b3		.stamphog/policy.yml @ 5ac5892 · reviewed head 9926f2e