fix(ui): dismissable multi-device note; drop synthetic category tag from search results

[TimeToBuildBob]

Two of the "Minor" items from #1058.

• Multi-device note — "Browser and stopwatch data are only available when viewing a single device." showed on every multi-device Activity view. It is now a small dismissable info alert; the dismissal persists in localStorage (aw-multidevice-note-dismissed), same approach as the supporter nudge on Home. The logic lives in src/util/multideviceNote.ts so it is unit-tested (Activity.vue itself does not load under jest).
• Search $category: ["searched"] tag — the search query categorizes every event into a synthetic searched category to filter on it, and that leaked into each result row. Results now drop $category.

Not in this PR, with reasons

• Browser apps always Uncategorized in Top Applications: root cause is structural, not a rule bug. app_events is merge_events_by_keys(title_events, ["app"]), which keeps only app, so the app row is classified from the app name alone. Rules match titles (GitHub, YouTube, …), and a browser's name matches none of them. Fixing it means picking a semantics: dominant category of the app's title events, or a per-app category from cat_events. That's a design call, so I'd rather not guess it in a minor-items PR.
• Bar label contrast on bright colors: already implemented in fix(dark-mode): restore appsummary bar-chart label contrast #1002 (per-bar luminance label colour, clipping for labels that overflow the bar), which is open and green.
• Sunburst label clipping and calmer default palette: not touched here.

Verification

• jest test/unit/multideviceNote.test.js: 2 passed
• eslint clean on changed files, tsc --noEmit clean, vue-cli-service build succeeds (this is the check that the pug template compiles)
• Not verified visually: no multi-device screenshot in this PR

[greptile-apps]

Confidence Score: 5/5

[Low risk] Adds dismissable UI note and filters search results.

The PR appears safe to merge; no actionable issues were found.

What we checked:

• Storage errors do not crash Activity: Both storage calls catch errors. The page still hides the note for the current view if saving fails.

Summary

Makes the multi-device note dismissible and saves that choice in localStorage. Removes the synthetic $category field from search results.

• Adds unit tests for the saved dismissal choice.
• No actionable issues found.
• Runtime tests and visual checks were not performed during this review.

_{Reviews (1) · Last reviewed commit: "fix(ui): dismissable multi-device note; ..."}

[codecov]

Codecov Report

❌ Patch coverage is 87.50000% with 1 line in your changes missing coverage. Please review.
✅ Project coverage is 63.35%. Comparing base (95cd6b4) to head (8c8c8d8).

Files with missing lines	Patch %	Lines
src/util/multideviceNote.ts	87.50%	1 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##           master    #1062      +/-   ##
==========================================
+ Coverage   63.30%   63.35%   +0.05%     
==========================================
  Files          52       53       +1     
  Lines        3608     3616       +8     
  Branches      892      887       -5     
==========================================
+ Hits         2284     2291       +7     
+ Misses       1309     1244      -65     
- Partials       15       81      +66     

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[TimeToBuildBob]

CI-green and mergeable (Greptile 5/5) — waiting only on a maintainer click.

This PR is ready to merge, but the bot has pull-only access to this repo and can't self-merge — surfacing it here so it isn't lost. The monitoring loop will stop re-flagging it now that this note is posted.