Only install skills for clients detected on the system

[samuv]

Summary

• When thv skill install runs without --clients (or with --clients=all), skills were extracted to directories for every client with SupportsSkills: true in the static config (~20 clients), regardless of whether those clients are actually present on the system.
• Add IsClientInstalled to ClientManager — uses the same os.Stat path check already present in GetClientStatus — and refactor GetClientStatus to call it.
• Filter clientPathAdapter.ListSkillSupportingClients() to only return clients that pass IsClientInstalled, so the default install targets only the clients that exist on the machine.
• Improve the error returned when no installed clients are detected to guide users toward --clients as an explicit override (also corrects the HTTP status from 500 to 400).

Type of change

• Bug fix (non-breaking)

Test plan

• Unit tests (task test)
• Linting (task lint-fix)

Changes

File	Change
pkg/client/discovery.go	Add IsClientInstalled(clientType ClientApp) bool; refactor GetClientStatus to call it
pkg/client/discovery_test.go	Add TestIsClientInstalled covering settings-file present, dir present, dir absent, and unregistered client
pkg/api/server.go	Filter clientPathAdapter.ListSkillSupportingClients to installed clients only; log skipped clients at debug
pkg/skills/skillsvc/skillsvc.go	Improve empty-clients error message and return 400 instead of 500

Does this introduce a user-facing change?

Yes — thv skill install <skill> no longer writes to directories for clients that aren't installed. Users with no detected clients get a clear error message suggesting --clients as an override. Explicit --clients=<name> continues to work regardless of detection.

[codecov]

Codecov Report

❌ Patch coverage is 57.14286% with 9 lines in your changes missing coverage. Please review.
✅ Project coverage is 69.25%. Comparing base (3c5ac7e) to head (9649782).
⚠️ Report is 1 commits behind head on main.

Files with missing lines	Patch %	Lines
pkg/api/server.go	0.00%	6 Missing ⚠️
pkg/skills/skillsvc/skillsvc.go	0.00%	3 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #4899      +/-   ##
==========================================
+ Coverage   69.21%   69.25%   +0.03%     
==========================================
  Files         533      533              
  Lines       55257    55266       +9     
==========================================
+ Hits        38246    38272      +26     
+ Misses      14068    14052      -16     
+ Partials     2943     2942       -1     

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