feat(tui): #275 unified Action Registry — one table feeds palette, slash, leader-chord

[windoliver]

Summary

Closes #275. Makes a single persistent ActionRegistry the one input to the TUI command palette, slash surfaces, and keyboard leader-chord resolver — every user-invocable action registers in one place. Built via spec → plan → subagent-driven TDD (design + plan in docs/superpowers/).

Backbone

• New Action registry (src/tui/actions/registry.ts): static descriptors + dynamic sources ((ctx) => Action[]); register/registerDynamic/setBindings/list/byId/search. Built once; live state flows via ctx at call time.
• Built-ins split into static actions + dynamic per-entity sources (builtin-actions.ts, dynamic-sources.ts, register-builtins.ts).
• Keybind → Action bridge (keymap/keymap-action-map.ts): keymap dispatches through registry.byId(...).run(ctx); the 50-case executeKeymapAction switch is retired. Remapping a key updates both dispatch and the palette cheatsheet (keymap stays the binding source of truth).
• Palette renders keybind column + suggested-first + greyed disabled rows with a reason footer.
• Leader chords get a 2s modal window + candidate-continuation overlay.

Slash (both surfaces)

• / opens the palette pre-filtered to slash-bearing actions.
• : opens a vim-style command-line (slash-input.tsx, InputMode.SlashCommand) parsing :cmd args → run(ctx, args).

MCP prompts — Grove MCP server exposes prompts from the repo prompts/ dir (prompts: {} capability, wired into serve.ts/serve-http.ts); TuiPromptProvider.listMcpPrompts; a prompt.* source surfaces them in a Prompts group; invoking delivers the template to the selected agent via the messaging/IPC path (never tmux).

Skills — listAvailableSkills (bundled skills/ + topology); TuiSkillProvider; a skill.request.* source in a Skills group, scoped to the selected agent slot's role; invoking asks the agent to acquire the skill via messaging/IPC.

Non-goal: inline docks (#193) — the agent-interaction actions are registered so docks can consume them later, but dock UI is unchanged.

Test Plan

• bun run typecheck — 0 errors
• bun test src/ — 7234 pass / 0 fail
• bun run build — succeeds
• Unit coverage for registry, dynamic sources, keybind bridge + dispatch parity (every retired TuiActionId runs the same effect), leader-chord, slash index + both surfaces, MCP prompt loader/provider/source, skill enumeration/provider/scoped source
• Manual TUI smoke: palette keybind/suggested/reason; remap reflects in palette; space leader overlay + 2s timeout; / filtered palette + :cmd; Prompts group delivers to agent; Skills group scoped to role