docs(structure): govern .planning/ and register the ops runbook

- docs/STRUCTURE.md: add a .planning/ registry (vision/roadmap/history/breakdown
  roles), broaden the roadmap role, add enforcement items 8-10.
- tools/check_requirements.py: scan .planning/ too - every .planning/**.md must be
  registered, registered files must exist, requirement rows rejected there.
- .planning/: PROJECT.md, ROADMAP.md, MILESTONES.md, and milestones/v0.5/M3/
  {roadmap.md,task_breakdown.md}. M3 breakdown holds only the tasks; decisions live
  in the contracts.
- docs/DEPLOYMENT.md: add the ops runbook (registered as ops).

docs/STRUCTURE.md

@@ -1,7 +1,7 @@
 # Structure contract
 
-This file defines the shape of the `docs/` system and how requirements enter it.
-`tools/check_requirements.py` enforces it.
+This file defines the shape of the `docs/` system and the `.planning/` tree, and how requirements
+enter it. `tools/check_requirements.py` enforces it.
 
 If the repo and this file disagree, fix one deliberately. Do not let them drift.
 
@@ -21,6 +21,7 @@ Every Markdown file under `docs/` is registered here. `docs/archive/**` and `doc
 | `docs/capabilities/CREATE.md` | capability |
 | `docs/contracts/CONTENT-WOO.md` | contract |
 | `docs/UAT-PRACTICE.md` | practice |
+| `docs/DEPLOYMENT.md` | ops |
 | `docs/capabilities/README.md` | index |
 | `docs/contracts/README.md` | index |
 | `docs/contracts/WOO-API.md` | contract |
@@ -30,6 +31,18 @@ Every Markdown file under `docs/` is registered here. `docs/archive/**` and `doc
 | `docs/contracts/UX.md` | contract |
 | `docs/contracts/TEST-SPEC.md` | contract |
 
+Every Markdown file under `.planning/` is registered here. `.planning/` holds planning artifacts
+only and is **not** a second requirements home: `docs/REQUIREMENTS.md` and `docs/MILESTONES.md`
+remain the point of record, and `.planning/` files cite requirement IDs without defining them.
+
+| Path | Role |
+|---|---|
+| `.planning/PROJECT.md` | vision |
+| `.planning/ROADMAP.md` | roadmap |
+| `.planning/MILESTONES.md` | history |
+| `.planning/milestones/v0.5/M3/roadmap.md` | roadmap |
+| `.planning/milestones/v0.5/M3/task_breakdown.md` | breakdown |
+
 Roles:
 
 - **index** — navigation only.
@@ -40,6 +53,11 @@ Roles:
 - **capability** — behavior and acceptance for one capability; cites IDs, does not define them.
 - **contract** — cross-cutting interface detail; cites IDs, does not define them.
 - **practice** — human walkthrough.
+- **ops** — runbook for hosts, builds, and release; cites inventory and contracts, defines no requirements.
+- **vision** — overall project vision and current state; cites IDs, defines none.
+- **roadmap** — version or milestone objectives; cites IDs, defines none.
+- **breakdown** — ordered task list for a version or milestone; cites IDs, defines none.
+- **history** — historical log of shipped milestones; cites IDs, defines none.
 
 ## ID namespaces
 
@@ -90,6 +108,9 @@ Nothing outside `REQUIREMENTS.md` may define a requirement. Capability and contr
 5. `Test` references resolve: a path given for a `shipped` requirement exists; an ID given resolves to a defined requirement; `—` is allowed.
 6. Requirement rows appear only in `REQUIREMENTS.md`.
 7. Every ID listed in `MILESTONES.md` exists in `REQUIREMENTS.md`.
+8. Every `.planning/` Markdown file is registered above.
+9. Every registered `.planning/` file exists on disk.
+10. Requirement rows appear nowhere outside `REQUIREMENTS.md`, including `.planning/`.
 
 ## Phase 2 migration (complete)