feat: everything-is-a-plugin, mandatory + optional (009)

[fatherlinux]

Summary

Unifies Acquacotta's feature model so Pomodoro, Settings, and Todos are all first-class plugins listed uniformly. Two are mandatory — always registered/enabled, non-toggleable, MCP tools always available — while Todos stays optional with the per-user enable/disable from spec 008.

Completes the plugin architecture started in 007 (per-user storage) and 008 (per-user optional plugins). See specs/009-mandatory-plugins/spec.md.

Changes

• plugin_registry: mandatory flag on registration; list_plugins reports it and forces mandatory→active; is_mandatory(); get_mcp_tool_registrars() now returns (id, registrar, mandatory) triples.
• Pomodoro/Settings as plugins: pomodoro_tools gains PLUGIN_METADATA (mandatory) and registers in app.py + mcp_server.py; Settings registered as a mandatory metadata-only plugin. Removed the hardcoded pomodoro_tools.register_mcp_tools — Pomodoro's tools now flow through the same registrar path, ungated because mandatory.
• app.py: /api/plugins/toggle returns 403 for a mandatory plugin.
• index.html: mandatory rows render checked + disabled with a "Required" badge; pluginEffectiveActive() always-true for mandatory.

No data-format change, no migration (FR-009).

Test plan

• 220 unit tests pass; ruff (check + format) clean
• Registry mandatory flag / always-active / is_mandatory; /api/plugins lists pomodoro/settings/todos with correct flags; mandatory toggle → 403; Todos toggle → 200; MCP registrars gate mandatory ungated + optional per-user
• Web verified live: Plugins list shows all features; Pomodoro/Settings locked "Required"; Todos toggleable; Timer/Settings tabs unaffected
• MCP server boots clean with Pomodoro registered ungated
• MCP end-to-end with a token — verify Pomodoro tools work regardless of Todos state (in prod)

🤖 Generated with Claude Code

[github-actions]

Gatehouse found no issues.

[gemini-code-assist]

Code Review

This pull request implements the 'Everything-is-a-Plugin' model (spec 009), introducing mandatory plugins (Pomodoro and Settings) alongside optional ones (Todos). It updates the plugin registry, the web UI, and the MCP server to ensure mandatory plugins are always active and cannot be disabled, while optional plugins remain toggleable per-user. Feedback on the changes highlights an issue in the toggle API endpoint where attempting to enable an already active mandatory plugin is incorrectly blocked with a 403 Forbidden error; the check should be refined to only restrict disabling actions.

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[gemini-code-assist]

The current check blocks any toggle request for a mandatory plugin, even if the request is attempting to enable it (enable=True). This results in a 403 Forbidden error with the message 'pomodoro' is a required plugin and cannot be disabled when a client attempts to enable an already active mandatory plugin. We should only restrict the toggle when enable is False (i.e., an attempt to disable it).

Suggested change

	if plugin_registry.is_mandatory("extension", plugin_id):
	return jsonify(
	{"error": f"'{plugin_id}' is a required plugin and cannot be disabled"}
	), HTTPStatus.FORBIDDEN
	if plugin_registry.is_mandatory("extension", plugin_id) and not enable:
	return jsonify(
	{"error": f"'{plugin_id}' is a required plugin and cannot be disabled"}
	), HTTPStatus.FORBIDDEN

[github-actions]

Gatehouse found no issues.