fix(skills): persist per-skill toggles in Antares configuration

[elliottophellia]

Changes

• Store profile-wide enable/disable preferences in skills.disabled, keyed by exact, case-sensitive skill name. Toggles persist atomically and publish live state without rewriting skill files; missing names retain preferences.
• Import legacy configured enabled: false headers once using skills.frontmatter_migrated. Incomplete imports abort startup/reload without marking migration complete. Environment-only settings are not persisted by these helpers.
• Block disabled entries across the agent skill tool's list, search, read, and chains operations. Search filters before ranking/limits; administrative APIs and /skills retain off entries. Content saves do not re-enable names.
• Serialize HTTP toggles through persistence and reload, use current manager snapshots after runtime replacement, and return persistence/publication errors.
• Show toggle failures inline in the Skills page, reconcile after errors, and disable page switches during a pending request.

Boundaries

skills.enabled remains the independent global gate. Disabling cannot retract model context already sent and does not restrict generic filesystem tools. A successful save followed by failed reload remains persisted but returns HTTP 500.

This branch starts from main and is independently reviewable from #42. Compatible changes were separately appended to the discovery branch with source-SHA provenance; this PR does not include automatic discovery or project scoping.

Checkpoints

1. 30e08ff — configuration persistence, migration, effective state, and HTTP publication.
2. 0980eb5 — disabled skill-tool access enforcement.
3. a380abd — dashboard persistence-error handling.

Verification

Passed with Go 1.26.7:

• go test ./...
• go test -race ./internal/config ./internal/skills ./internal/agent ./internal/commands ./internal/server ./cmd/antares
• make build build-fixture
• Frontend bun test: 86 passed, 0 failed.
• Isolated real-binary smoke with scrubbed HOME/config environment and loopback SSE provider: one-time migration, toggles, restart, generic config updates, real skill-tool outputs/prompts, and administrative off-state visibility.
• Source bytes, permissions, and mtime unchanged by toggles, including read-only source fixtures; concurrent toggles preserve both preferences; malformed config and atomic-save/reload failures exercise error paths.
• Browser interactions at 1440×900 and 390×844: checked-state persistence, pending-request guard, and real config-directory permission failure producing an inline alert with unchanged checked state and no unhandled page error.
• Mutation proofs detect source rewrites, disabled body access, and enabled results displaced behind 30 disabled search matches. Restored tests pass.

The existing DNS-dependent TestValidateCustomProviderBaseURL intermittently timed out resolving openrouter.ai; final full and race suites passed. Unmodified make smoke was not used as feature proof because its fixture disables skills.

Please do not merge yet.

[enowdev]

Shipped in main as part of #42 rather than as a separate merge.

#42 is a strict superset of this branch: all 22 files here are also in #42, and internal/config/skills.go and internal/tools/skill.go are byte-identical between the two. Every feature of this PR is present in main — skills.disabled persistence, MigrateSkillState / frontmatter_migrated one-time import, SetSkillEnabled, Manager.SetDisabled / LegacyDisabled, Filter.EnabledOnly search filtering, skillsConfigMu-serialized HTTP toggles, and the Skills page inline error handling.

Test coverage carried over too. Two of this branch's tests exist under names adapted to #42's architecture, and both pass:

• TestSkillHandlersObserveManagerReplacedDuringReload → TestSkillHandlersObserveInPlaceReconfigure (feat(skills): automatically discover and refresh project-scoped skills #42 reconfigures the manager in place instead of swapping the pointer)
• TestLegacyDisabledUsesSelectedWinnerAndSortsNames → TestLegacyDisabledUsesConfiguredWinnerAndSortsNames

Verified on the merged tree: go build ./..., go vet ./..., full go test ./..., go test -race over config/skills/agent/server/commands/tui/tools/cmd, make build, and frontend bun test (86 passed) + typecheck + build.

Noted your "please do not merge yet" — this closes as delivered-via-#42, not as a merge of this branch. Nothing here is dropped. Reopen if you intended changes beyond what #42 carried.

Review note carried forward: SetSkillEnabled hard-errors when migration has not run, and migration only runs from cmd/antares bootstrap/reload. Both server.New call sites live there today, so it is not reachable now, but it leaves internal/server depending on a cmd-level init step.