Single canonical document for new contributors and operators. Cleans
up stale documentation and replaces it with a coherent architecture
+ decision-log narrative.

What landed:

* **`docs/DESIGN.md`** (new, ~600 lines) — the consolidated design
  document. Sixteen sections covering: what the framework is, the
  layered architecture (LangGraph + LangChain + FastMCP +
  framework + app), core abstractions (Session, Skill, AgentRun,
  ToolCall, Orchestrator, Gateway, AgentTurnOutput), runtime model
  (lifecycle, dispatch, routing, termination), LLM provider story
  (per-agent override, 429 retry, live verification), markdown
  turn-output contract (the 7 parse paths + gpt-oss quirks), HITL
  approve/reject (langgraph 1.x __interrupt__ semantics + the five
  PR #6 fixes), storage, telemetry, deployment, decision log
  (12 numbered DEC-NNN entries with rationale), milestone history
  (v1.0–v1.5), pending list, and a "where to find what" map.

* **`README.md`** (new, repo root) — short overview pointing at
  docs/DESIGN.md as the canonical entry. Quickstart commands, two
  example apps named, document map.

* **`examples/incident_management/README.md`** — slimmed from
  ~230 lines to ~80. Removed framework-wide content (Phase 4/5/6/8/9
  narrative, agent kinds explainer, trigger registry walkthrough,
  genericity ratchet description) — all of that lives in
  docs/DESIGN.md now. App README focuses on the layout, domain
  shape, MCP tools, ASR memory layers.

* **`examples/code_review/README.md`** — slimmed from ~120 lines to
  ~70. Same treatment: framework explainer text moved to DESIGN,
  README focuses on app-specific details.

* **`.gitignore`** — explicitly track `docs/DESIGN.md` next to the
  other two committed docs (`AIRGAP_INSTALL.md`, `DEVELOPMENT.md`).
  The `docs/*` blanket ignore stays so accidentally-generated scratch
  doesn't leak in.

* Deleted four committed `.planning/phases/*` artifacts (Phase 01
  summary, Phase 14 plan / summary / verification). Their content is
  superseded by docs/DESIGN.md § 13 (milestone history) and § 12
  (decision log). The `.planning/` directory is gitignored
  per-convention; these were committed before that convention
  applied.

`docs/DEVELOPMENT.md` and `docs/AIRGAP_INSTALL.md` are unchanged —
they're operational how-tos (regenerate dist, install behind a
mirror) rather than design content, and remain accurate.

Suite: 1265 passed (unchanged), ruff clean. No source changes.