kb: retire pi-installation association (OMP is the primary harness)

Purge live-state claims that ~/.pi is our harness; keep general
pi documentation in omp-docs/ and dated historical records.

- README.md: single config source; Legacy Notes reworded
- AGENTS.md: drop 'like ~/.pi did' framing
- APPEND_SYSTEM.md: okf-spec -> omp-docs/references/okf-spec.md
- dotfiles/zsh/.zshrc: systemprompt alias -> APPEND_SYSTEM.md
- managed skill llm-fleet-model-swap + model_config_sync skill:
  single-source models.yml; validation script YAML-only
- memories (MEMORY.md, memory_summary.md, learned.md): single source
- omp-docs: .okf root -> ~/.omp/omp-docs; de-live pi-era claims in
  pi/index.md, pi-web-access.md, engineering/agents-files.md

AGENTS.md

@@ -68,7 +68,7 @@ secret in every agent's context window on every machine that pulls this repo.
   repo's operator: never stop, mask, or restart it (or any production service on
   any box) without an explicit, current, per-run OK from Frank.
 
-## File-organization doctrine (why this repo won't rot like ~/.pi did)
+## File-organization doctrine (why this repo stays readable)
 
 - One concept, one file; directories get an `index.md` listing their contents —
   that's the OKF contract, and it is also the anti-rot mechanism: nothing may