docs(governance): add ADR 0006 OpenAI shim scope + Class A/B taxonomy (#100)

Introduces an explicit two-class taxonomy of OCP endpoints to resolve
the structural ambiguity surfaced by PR #99 (external response_format
honoring on /v1/chat/completions):

- Class A: cli.js-mirror endpoints. Rules 1-5 of ALIGNMENT.md apply
  verbatim. Citation requirement unchanged (cli.js:NNNN). The 2026-04-11
  drift discipline is preserved without weakening.

- Class B: OCP-owned compatibility endpoints. Anchored to OpenAI's
  /v1/chat/completions specification (B.1) or to an authorizing ADR
  (B.2). Citation shifts to spec section + ADR number. Class B inherits
  the same anti-invention discipline; the anchor differs.

Grandfather provision in ADR 0006 retroactively authorizes the 12
existing B.2 administrative endpoints at v3.16.4 behaviour (one-time,
contract-frozen). New B.2 endpoints or any new method on a grandfathered
endpoint requires its own ADR per Rule 4 (Class B mapping).

Changes:
- new: docs/adr/0006-openai-shim-scope.md
- new: docs/openai-compat-pin.md (placeholder for first B.1 audit)
- mod: ALIGNMENT.md (Class B section, rule mapping table, updated
  Unalignable Policy and Annual Audit scope; Rules 1-5 byte-identical)
- mod: .github/PULL_REQUEST_TEMPLATE.md (Endpoint Class radio, separate
  evidence sections for A vs B, reviewer checklist updated)
- mod: docs/adr/README.md (index entry for ADR 0006)

Independent reviewer (fresh-context opus per Iron Rule 10) verified:
all 12 load-bearing checks pass — Rules 1-5 byte-identical to
origin/main, 2026-04-11 drift narrative unchanged, explicit
non-relitigation safeguard present in ADR 0006, grandfather provision
narrowly scoped, Class B inventory matches server.mjs reality (14/14),
single governance layer per Iron Rule 11 (no server.mjs touch),
alignment.yml unmodified. Verdict: APPROVE_WITH_MINOR with 3 of 5
non-blocking suggestions folded in (operations-vs-endpoints precision,
PR template Hybrid wording, openai-compat-pin.md stub).

Triggering incident: PR #99 by external contributor (response_format
honoring on /v1/chat/completions). This governance PR ships separately
per Iron Rule 11 (IDR); the feature PR #99 will rebase on this and
declare Class B with ADR 0006 citation.

Co-authored-by: dtzp555 <dtzp555@gmail.com>
Co-authored-by: Claude Opus 4.7 <noreply@anthropic.com>

docs/adr/README.md

@@ -22,6 +22,7 @@ New ADRs increment from the highest existing number. Filenames are
 | [0003](0003-models-json-spot.md) | `models.json` as SPOT | Why model IDs / aliases / context windows live in a single JSON file (not duplicated in `server.mjs` and `setup.mjs` arrays). v3.11.0 refactor. |
 | [0004](0004-openclaw-auto-sync.md) | OpenClaw Auto-Sync | Why `scripts/sync-openclaw.mjs` runs on `ocp update`, what its scope boundary is (writes only `models.providers["claude-local"].models` and `agents.defaults.models["claude-local/*"]`), and the idempotency contract. |
 | [0005](0005-no-multi-provider.md) | No Multi-Provider | Why OCP stays single-provider (Anthropic-via-cli.js) and does not extend to OpenAI / Gemini / OpenRouter. Cost estimate: ~7 weeks for a v1 that buys neither moat nor commercial readiness. Separate commercial work starts in a separate repo. |
+| [0006](0006-openai-shim-scope.md) | OpenAI Shim Scope | The Class A / Class B taxonomy. Class A endpoints (`cli.js`-mirror) keep Rules 1–5 verbatim; Class B endpoints (OCP-owned compatibility surface — `/v1/chat/completions`, `/v1/models`, admin endpoints) are anchored to OpenAI's spec (B.1) or to an authorizing ADR (B.2). Triggered by PR #99 (external `response_format` honoring). Grandfathers the existing B.2 inventory at v3.16.4. |
 
 ## When to write a new ADR