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

agent/memories/--home-dank-.omp--/skills/model_config_sync/examples/context_update_example.md

@@ -1,5 +1,5 @@
 When updating context from 160k to 200k:
 1. Convert to Ki: 200 × 1024 = 204800
-2. Update `contextWindow` and `maxTokens` in both `~/.pi/agent/models.json` and `~/.omp/agent/models.yml`
+2. Update `contextWindow` and `maxTokens` in `~/.omp/agent/models.yml`
 3. No cache flush required; applies on next config read.
 4. Validate with validation script.