docs(skills): all skill packs are gitignored, none committed

The owner added /.agents/skills/ to .gitignore, so no skill is in the repository:
the UE packs, the cpp router and blender-director are all local-only. Reconcile the
docs that still said 'in the repository':

- AGENTS.md: blender-director and the UE packs now say gitignored, not committed.
- Docs/toolchain.md: drop the stale 'in this repository' row and name the UE and C++
  sources in the table.
- MEMORY.md: record the decision.

AGENTS.md

@@ -181,7 +181,7 @@ Always use a consistent scale test, named export presets, and repeatable import
 
 The 93 upstream Blender skill packs (MIT, blender-skills 1.3.0) live once, in the **common** agent folder `~/.pi/agent/skills/`, together with the shared `references/` notes and the upstream `LICENSE`. They are agent instructions, not add-ons, and nothing in the pipeline depends on them.
 
-Only the project-specific pack stays in the repository: `.agents/skills/blender-skills/blender-director/` — the pipeline orchestrator, which names this project's tools and stages. It refers to the shared notes by absolute path (`~/.pi/agent/skills/references/…`).
+The project-specific pack, `.agents/skills/blender-skills/blender-director/` — the pipeline orchestrator, which names this project's tools and stages — also stays **out of the repository**: `/.agents/skills/` is gitignored. It refers to the shared notes by absolute path (`~/.pi/agent/skills/references/…`).
 
 Do not copy the common packs into the repository: a second copy under a different root is a name collision, and Pi keeps the first one it finds and warns on every start. Add a pack to `~/.pi/agent/skills/<pack>/SKILL.md` (one level down, flat) and it is picked up everywhere; `references/` sits beside them at `~/.pi/agent/skills/references/`.
 
@@ -199,7 +199,7 @@ Do not copy the common packs into the repository: a second copy under a differen
 
 ## Unreal Engine skills
 
-The 31 Unreal Engine skill packs (MIT, [quodsoler/unreal-engine-skills](https://github.com/quodsoler/unreal-engine-skills) `f3742d7`) live in the repository at `.agents/skills/ue-*/` and target **UE 5.8 C++**. Each carries API examples verified against the 5.8 headers plus a deprecated-API table that maps old calls to the 5.8 forms. They are agent instructions, not add-ons.
+The 31 Unreal Engine skill packs (MIT, [quodsoler/unreal-engine-skills](https://github.com/quodsoler/unreal-engine-skills) `f3742d7`) live locally at `.agents/skills/ue-*/` (gitignored, not committed) and target **UE 5.8 C++**. Each carries API examples verified against the 5.8 headers plus a deprecated-API table that maps old calls to the 5.8 forms. They are agent instructions, not add-ons.
 
 `.agents/skills/ue-project-context/` is the entry point: it writes `.agents/ue-project-context.md` (module names, conventions, enabled plugins), and every other UE skill reads that file first. Refresh it when the project changes — new module, new plugin, engine bump — before consulting the rest.