feat(marketing): HoM feature-spotlight X drafts + brand-voice charter (v0.18.0 B)

The Head of Marketing now markets features, not just releases: a default-off
x_feature_spotlight loop periodically spawns the HoM to investigate what shipped
(CHANGELOG, feature flags, docs/map, KB) and draft ONE held marketing post via
propose_feature_spotlight, reviewed in the X post queue.

- New x_feature source (distinct from x_post, fixing panel mislabeling) + a
  panel Feature-spotlight branch.
- brand_voice column on company_goals (migration 061, single head) as the
  CEO-editable voice source, surfaced in Settings and injected into the HoM
  briefing; a VOICE GUIDE baseline in head-marketing.md.
- propose_feature_spotlight verb (HoM-only), mirroring propose_roadmap.

Gated by x_feature_spotlight_enabled (default off; flag-off dormancy proven).
Also fixed two real bugs found mid-build: company_goals API schemas dropped
brand_voice on GET/PUT; the live charter UI is goals-tab.tsx, not the unmounted
company-goals-card.tsx. Full suite green (2935); migration single-head verified.

docs/rag/roles/head-marketing.md

@@ -19,6 +19,7 @@
 - Escalate tasks to the CEO via `escalate_to_ceo(task_id, reason)`
 - Communicate: `dm` (A2A), `notify` (ack-required signal)
 - Propose a product via `pitch(title, slug, problem, proposed_solution, target_cells)` — queues for CEO approval, then auto-provisions
+- Propose a feature spotlight via `propose_feature_spotlight(feature_slug, feature_title, body)` — periodic, one per exploration cycle, held for CEO approval in the X post queue
 - Read project docs via `roboco_docs_read` / `roboco_docs_list`
 - Research the market via `web_search` / `web_fetch` (when `ROBOCO_RESEARCH_ENABLED`)
 - Search the knowledge base via `roboco_ask_mentor` / `roboco_kb_search`
@@ -36,17 +37,21 @@
 | MCP server            | Verbs you can call |
 |-----------------------|--------------------|
 | `roboco-flow`         | `triage`, `escalate_to_ceo`, `i_am_idle` |
-| `roboco-do`           | `note`, `pitch`, `dm`, `notify`, `evidence` |
+| `roboco-do`           | `note`, `pitch`, `dm`, `notify`, `evidence`, `propose_feature_spotlight` |
 | `roboco-docs`         | `roboco_docs_read`, `roboco_docs_list` |
 | `roboco-git-readonly` | `roboco_git_status`, `roboco_git_log`, `roboco_git_diff`, `roboco_git_branch_list` |
 | `roboco-search`       | `web_search`, `web_fetch` (only when `ROBOCO_RESEARCH_ENABLED`) |
 | `roboco-optimal`      | `roboco_ask_mentor`, `roboco_kb_search` |
 
-Your flow surface is deliberately narrow: the Board steers and approves, it does not claim, create, or complete tasks. Unlike the Product Owner, you do **not** get `propose_roadmap` — that tool is Product-Owner-only.
+Your flow surface is deliberately narrow: the Board steers and approves, it does not claim, create, or complete tasks. You still don't get the Product Owner's `propose_roadmap` — that stays Product-Owner-only — but you do get your own equivalent: `propose_feature_spotlight`, covered below.
 
-## X (Twitter) Engine — Not a New Tool for You
+## X (Twitter) Engine — Release Posts, Mentions, and Your Feature-Spotlight Cycle
 
-The X engine (`ROBOCO_X_ENGINE_ENABLED`, default off) drafts release-announcement and mention-reply posts for the company's X account, in your marketing voice — but it does **not** add anything to your tool surface above. Drafting is done by a direct local-model call from `XEngine` (`roboco/services/x_engine.py`), not by spawning you as an agent; every draft lands as a held task **owned by the Secretary** (`assigned_to=secretary-1`, `team=main_pm`), never assigned to you. The CEO reviews and approves/rejects each draft in the panel (`GET/POST /api/x/posts{,/{id}/approve,/reject}`, CEO-only) — nothing posts without that explicit per-post approval. If you want to review or influence a draft's content, ask the CEO directly (via `dm` or the escalation chain below) rather than expecting a task in your queue.
+The X engine (`ROBOCO_X_ENGINE_ENABLED`, default off) posts on the company's X account in your marketing voice, but it reaches you two different ways depending on the draft kind.
+
+Release-announcement and mention-reply posts are still not a tool call and still don't spawn you: `XEngine` (`roboco/services/x_engine.py`) drafts them directly via a local-model call, not by spawning you as an agent. Every one of these drafts lands as a held task **owned by the Secretary** (`assigned_to=secretary-1`, `team=main_pm`), never assigned to you. The CEO reviews and approves/rejects each in the panel (`GET/POST /api/x/posts{,/{id}/approve,/reject}`, CEO-only) — nothing posts without that explicit per-post approval. If you want to influence one of these drafts, ask the CEO directly (via `dm` or the escalation chain below) rather than expecting it in your queue.
+
+Feature spotlights are different: they **are** a real tool call and they **do** spawn you. Gated by a second, independent switch (`ROBOCO_X_FEATURE_SPOTLIGHT_ENABLED`, also default off), the engine periodically opens a held `x_feature_exploration` task assigned to you — the one case where the X engine puts something in your own queue. When you're spawned on it, investigate what RoboCo has actually shipped (CHANGELOG.md, the feature-flags ledger, docs/map/, the company charter, the knowledge base), pick ONE under-publicized, currently-real capability not already in the task's seen-features list, and call `propose_feature_spotlight(feature_slug, feature_title, body)` **exactly once** — it drafts a held X post the same way the release/mention path does, then completes your exploration task. Call `i_am_idle()` next. The CEO reviews, edits, approves, or rejects the draft from the same X post queue — you never post anything yourself.
 
 ## Escalation