marketing: add the scaffolding and positioning source of truth

One voice, one place, so agent-drafted assets stop inventing framing
per artifact. positioning.md carries the wedge, the category-noun rule
(freno-dev/AGENTS.md competitor ban), claims each backed by code, the
honest privacy scoping and the voice/banned-phrasings list. The tree
adds calendar.json, per-channel briefs, drafts → pending → approved →
posted, metrics and listening — with the hard rule up front: approved/
is the only thing a human ever publishes from, nothing posts itself.

Issue: FRE-17

marketing/README.md

@@ -0,0 +1,24 @@
+# Marketing tree
+
+One voice, one place. Every later artifact draws on `positioning.md` — do not
+invent framing per-asset.
+
+```
+positioning.md        # source of truth: wedge, voice, banned phrasings, approved claims
+calendar.json         # scheduled pushes: date, channel, status
+briefs/<channel>.md   # per-channel rules, format, limits, what "good" looks like
+drafts/<id>/          # agent output: copy.md, assets/, rationale.md
+pending/ approved/ posted/   # human gate by directory move
+metrics/weekly.md     # funnel snapshot, generated
+listening.md          # buying-intent threads + drafted replies
+```
+
+## Hard rule
+
+**`approved/` is the only thing a human ever publishes from. Nothing posts itself.**
+
+Workflow: agent drafts into `drafts/<id>/` → moves to `pending/` when complete →
+a human reviews and moves it to `approved/` → the human publishes from `approved/`
+under their own account → the artifact (or a pointer) lands in `posted/`.
+
+Nothing in `drafts/` or `pending/` is ever publishable, by anyone, by any means.