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.

Docs/toolchain.md

@@ -34,10 +34,12 @@ Unreal Engine 5.9 is in preview and Unreal Engine 6 has been announced as of Nov
 | Package | blender-skills `1.3.0`, upstream commit `8f778d2`, MIT |
 | Source | <https://github.com/arjun988/blender-skills> |
 | Location | Local only, common root: `~/.pi/agent/skills/` (93 packs, `references/`, `LICENSE`) — not distributed with the repository |
-| Project-specific | `.agents/skills/blender-skills/blender-director/` in this repository |
+| Project-specific | `.agents/skills/blender-skills/blender-director/` (gitignored, not committed) |
 | Installed | 2026-11-06, copied from a local checkout of `.claude/skills/` without edits; flattened to the common root on 2026-11-10 |
+| UE skills | `quodsoler/unreal-engine-skills` `f3742d7`, MIT — 31 packs at `.agents/skills/ue-*/` (gitignored), target UE 5.8 C++ |
+| C++ skill | `DiamonDinoia/skill-cpp` `f2617fb`, MIT — `cpp` router at `.agents/skills/cpp/` (gitignored) |
 
-These are instructions and reference notes for agents, not code that runs in a build. Four of them assume a **Blender MCP server**; this project drives Blender headlessly through `bpy` (`Tools/*.py`) instead, so MCP is optional and nothing depends on it.
+All skill packs — Blender, Unreal and C++ — are agent instructions, not code that runs in a build, and **none are committed**: `/.agents/skills/` is gitignored and the Blender packs live in the common `~/.pi/agent/skills/` root. Four of the Blender packs assume a **Blender MCP server**; this project drives Blender headlessly through `bpy` (`Tools/*.py`) instead, so MCP is optional and nothing depends on it.
 
 To update: copy `.claude/skills/` from a newer upstream checkout over the local directory, then record the new version and commit hash in this table. Skills are read on demand, so the harness catalog may need a reload before they appear as first-class entries.