fix(categories): auto-select sole hostname in category builder

[TimeToBuildBob]

Problem

The category builder looks broken until you open Show options and pick a hostname (ActivityWatch/activitywatch#1389). Two things stacked:

1. queryOptions was initialized without hostname, and fetchWords() was not called on mount (commented as "Called by watch" without immediate: true).
2. The empty state for a missing hostname said install a watcher, which is the wrong diagnosis when buckets already exist.

Change

• After ensureLoaded(), auto-select the hostname when there is exactly one non-unknown host.
• If several known hosts exist (or only unknown), leave hostname unset and tell the user to open Show options.
• Keep the "install a watcher" copy only when bucketsStore.hosts is empty.
• Mount QueryOptions with v-if instead of v-show so it does not auto-pick hostnameChoices[0] while the panel is still collapsed.

Workaround (until this lands)

Open Show options and choose the device hostname.

Test plan

• npx jest --selectProjects node --testPathPattern hostnames.test.node
• One-host machine: category builder shows words without opening options
• Multi-host machine: empty state names Show options; picking a host loads words
• No buckets: still shows the install-a-watcher copy

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 49.55%. Comparing base (3cbe349) to head (f66c44b).

Additional details and impacted files

@@            Coverage Diff             @@
##           master     #950      +/-   ##
==========================================
+ Coverage   49.36%   49.55%   +0.18%     
==========================================
  Files          45       45              
  Lines        2769     2779      +10     
  Branches      625      629       +4     
==========================================
+ Hits         1367     1377      +10     
  Misses       1322     1322              
  Partials       80       80              

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[greptile-apps]

Greptile Summary

The PR makes the category builder automatically query activity when exactly one known hostname is available and provides more accurate empty-state guidance otherwise.

• Adds reusable helpers for selecting a sole known hostname and classifying hostname-related empty states.
• Defers mounting query options until the panel is opened.
• Adds unit coverage for hostname selection and empty-state classification.

Confidence Score: 5/5

The PR appears safe to merge, with no concrete blocking or non-blocking defects identified in the changed behavior.

The sole-host selection receives a deduplicated host list, reactive hostname assignment reaches the existing query watcher, and multi-host or unavailable-host states remain explicitly user-selectable.

Important Files Changed

Filename	Overview
src/views/settings/CategoryBuilder.vue	Coordinates bucket loading, sole-host selection, query triggering, options-panel mounting, and distinct no-host versus unselected-host messaging without an identified actionable defect.
src/util/hostnames.ts	Adds focused hostname filtering, sole-host selection, and empty-state helpers with behavior aligned to the category builder flow.
test/unit/hostnames.test.node.ts	Covers known, unknown, empty, and multi-host cases for the newly introduced utility behavior.

_{Reviews (1): Last reviewed commit: "fix(categories): auto-select sole hostna..." | Re-trigger Greptile}

[TimeToBuildBob]

CI-green and mergeable — 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.

[TimeToBuildBob]

Automated merge handoff for f66c44b0c9e4:

• CI gate: satisfied
• Review threads: clear
• Self-merge: blocked — pull-only access on this repo, and these paths are outside the allowlist:
• src/util/hostnames.ts
• src/views/settings/CategoryBuilder.vue

This head is ready for maintainer review and manual merge. Project monitoring marked it human_merge_required and will not spend retry sessions attempting an automated merge. A new head will be evaluated independently.