[VIVPM]

What & why

Skills → Browse can offer Install for a skill already discovered on disk.
Clicking it then fails with “Already installed”.

This change shows direct GitHub catalog entries as Installed when their
destination folder matches a discovered Claude skill. It reuses the
installer's URL parsing and folder validation, existing button styling,
and existing translation.

Matching uses folder identity rather than frontmatter names, so unrelated
skills with the same display name remain installable. OpenCode and Codex
plugins are excluded. Unresolved third-party catalog links are outside
this change's scope.

Addresses #793.

Type of change

• Bug fix

Evidence

The images below show actual test output rendered as images, not
screenshots of a running Electron app. Both runs use the same component
test and fixtures.

Before

On unchanged source, an already-installed skill showed:

skillsTab.install, disabled=false

The six-case component suite had 5 passes and 1 failure.

After

With the patch, the same skill showed:

skillsTab.installed, disabled=true

The same six-case suite had 6 passes and 0 failures.

How I tested it

Windows, Node.js 24.16.0:

• npm run typecheck — passed.
• Four focused Skills test files — 32 passed, including junction discovery.
• npm run build — passed.
• npm run test:focused — 940 passed, 23 failed, 14 skipped.

For comparison, the unchanged baseline at f797048 had 928 passed,
23 failed, and 14 skipped. The same 23 test names and error types
occurred in both runs; all 12 newly added tests passed. The failures
include Windows file-symlink permission errors, worktree dependency
tests, and unrelated source/configuration assertions.

Checklist

• Before and after evidence is attached above under both headings.
• npm run typecheck passes.
• npm run test:focused passes — baseline failures documented above.
• npm run build succeeds.
• This PR is one focused change.
• I reviewed the diff.
• The UI reuses existing styles and translations.
• No art was added or changed.