docs(skills): one common copy of the skill packs; project keeps blender-director

The 94 symlinks in ~/.agents/skills and the full second copy in
~/.pi/agent/skills/blender-skills were the same packs under two roots, so Pi
reported a collision for every one of them on every start and silently dropped
the loser.

- The 93 upstream packs, the shared references/ notes and the LICENSE now live
  once, flat and one level down, in the common agent folder ~/.pi/agent/skills/.
- The repository keeps only the project-specific pack:
  .agents/skills/blender-skills/blender-director/. Its ../references/ links now
  point at ~/.pi/agent/skills/references/ because it no longer sits beside them.
  Its SKILL.md declared metadata.role twice (specialist, orchestrator), which is
  fatal YAML - the pack had never actually loaded.
- AGENTS.md and Docs/toolchain.md describe the split and warn against copying the
  common packs back into the repository.

Verified by walking all three discovery roots and parsing every frontmatter:
97 skills loaded, 0 malformed, 0 collisions.

MEMORY.md

@@ -512,3 +512,11 @@ Scope: facts and traps that cost time to establish. Planned work lives in [TODO.
 - **A 1 cm solidify shell lets the body poke through.** Garments built by duplicating body faces needed 2 cm of solidify plus an 8 mm fatten along their own normals before the cloth read as continuous at shoulders, hips and knees.
 - **Warm skin sampling as blue-grey was lighting, not material.** The body stood in building shadow and was lit almost entirely by the blue `Demo_SkyLight` (intensity 2.6): face (99, 98, 100), arms (67, 74, 81). Raising the sun to pitch -74 moved the face to (131, 121, 117). A deliberate red test colour reaching the render first proved the material and the slot assignment were fine, which is what stopped a long hunt in the wrong place.
 - **The Unreal commandlet drops unknown command-line switches.** A `--unlit-test` flag passed after `-script` never reached Python; an environment variable does get through (and even that proved unnecessary once the red test settled the question).
+
+## 2026-11-10 — skills: one common copy, project-specific stays local
+
+- **Symlinked packs were the wrong fix.** The 2026-11-06 fix put 94 symlinks in `~/.agents/skills/<pack>` → the repo, while `~/.pi/agent/skills/blender-skills/` held a full second copy of the same packs. Pi keeps the first discovery and warns on every start: 94 "collision" lines. `~/.agents/skills/blender-skills/` (the upstream git checkout) also contains 94 packs under `.claude/skills/` and `.cursor/skills/` — inert, because dot-directories are not scanned.
+- **`blender-director/SKILL.md` never loaded.** It declared `role:` twice in `metadata` (`specialist` then `orchestrator`); duplicate YAML keys are fatal, so the pack was dropped silently while the other 94 loaded.
+- **Layout now** — shared, one level down and flat so it is discovered: `~/.pi/agent/skills/<93 packs>/`, `~/.pi/agent/skills/references/`, `~/.pi/agent/skills/LICENSE`. Project-specific and versioned: `.agents/skills/blender-skills/blender-director/`, whose `../references/` links were rewritten to `~/.pi/agent/skills/references/…` because it no longer sits beside them. The 94 `~/.agents/skills` symlinks are gone.
+- **Verified** by walking the three discovery roots (`~/.pi/agent/skills`, `~/.agents/skills`, project `.agents/skills`, dot-dirs skipped), parsing every frontmatter: **97 skills loaded, 0 malformed, 0 collisions**. Backup of the old trees: `/tmp/agent-skills-backup.tgz`.
+- Rule: a skill exists in **one** place. Two roots with the same `name` is a warning on every start, and the loser is invisible — check the startup list, not the file tree.