issue-42 tenant skills

AMCS2 MCP calls were attempted but cancelled by the environment, so this local fallback log captures the required thought summary.
Model selection: Tuesday Claude primary was unavailable because its OAuth access token expired; Codex gpt-5.5 was used as the final fallback.
tea issue 42 crashed before returning issue data, and Gitea DNS was unavailable, so the fix was inferred from the issue branch name and tenant-skill code paths.
Implemented tenant enforcement for project skill links in internal/store/skills.go: add, remove, and list now require the project and skill to belong to the active tenant when a tenant context is present.
Added focused tests for the tenant predicate helper in internal/store/skills_test.go.
Verification: go test ./internal/store -v, go test ./internal/tools -v, and go test ./internal/store ./internal/tools passed.
Full go test ./... was attempted but failed on existing environment constraints: missing ui/dist embedded assets and sandbox-blocked httptest listener sockets.