Add thv skill builds command to list and remove locally-built OCI skill artifacts

[samuv]

Summary

thv skill build packages a skill directory into a local OCI artifact, but there was no way to see or manage what had been built. This adds:

• thv skill builds — lists all locally-built OCI skill artifacts with tag, digest, name, and version
• thv skill builds remove <tag> — removes a locally-built artifact and garbage-collects its blobs when no other tag shares the same digest

Key design decisions

• ListBuilds filters by ArtifactType == "dev.toolhive.skills.v1" so that remotely-pulled skills sharing the local OCI store are not surfaced
• Metadata extraction (name, description, version) is best-effort: artifacts without parseable OCI config labels still appear with those fields empty
• DeleteBuild delegates to Store.DeleteBuild (toolhive-core v0.0.14) which handles orphaned-blob cleanup atomically — blobs are retained when another tag shares the same digest

Type of change

• New feature

Changes

File	Change
go.mod / go.sum	Bump toolhive-core to v0.0.14
pkg/skills/options.go	Add LocalBuild type
pkg/skills/service.go	Add ListBuilds and DeleteBuild to SkillService interface
pkg/skills/skillsvc/skillsvc.go	Implement ListBuilds (with ArtifactType filter), DeleteBuild, and isSkillArtifact helper
pkg/skills/skillsvc/skillsvc_test.go	7 tests for ListBuilds, 4 tests for DeleteBuild
pkg/skills/mocks/mock_service.go	Regenerated mock
pkg/api/v1/skills.go + skills_types.go	GET /builds and DELETE /builds/{tag} handlers
pkg/api/v1/skills_test.go	6 router tests for the new endpoints
pkg/skills/client/client.go + dto.go	ListBuilds and DeleteBuild HTTP client methods
cmd/thv/app/skill_builds.go	thv skill builds CLI command
cmd/thv/app/skill_builds_remove.go	thv skill builds remove CLI subcommand
docs/server/	Regenerated OpenAPI spec

Does this introduce a user-facing change?

Yes. Users can now run:

• thv skill builds to list locally-built artifacts
• thv skill builds remove <tag> to remove an artifact and its blobs

The same operations are available via the API at GET /api/v1beta/skills/builds and DELETE /api/v1beta/skills/builds/{tag}.

Special notes for reviewers

DELETE /builds/{tag} is registered as a more-specific route than the existing DELETE /{name} wildcard in the chi router, so there is no routing conflict. The 404 on a missing tag is propagated directly from Store.DeleteBuild in toolhive-core.

[codecov]

Codecov Report

❌ Patch coverage is 87.50000% with 2 lines in your changes missing coverage. Please review.
✅ Project coverage is 68.92%. Comparing base (8b8412b) to head (6cc3288).
⚠️ Report is 2 commits behind head on main.

Files with missing lines	Patch %	Lines
pkg/skills/client/client.go	0.00%	2 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #4674      +/-   ##
==========================================
+ Coverage   68.84%   68.92%   +0.07%     
==========================================
  Files         509      509              
  Lines       52668    52684      +16     
==========================================
+ Hits        36259    36310      +51     
+ Misses      13606    13570      -36     
- Partials     2803     2804       +1     

☔ View full report in Codecov by Sentry.
📢 Have feedback on the report? Share it here.

🚀 New features to boost your workflow:

• ❄️ Test Analytics: Detect flaky tests, report on failures, and find test suite problems.