Move docs/ package mirror into document-navigator plugin

Relocate the ~6k-file docs tree from the repo root into
plugins/document-navigator/docs/ so the plugin is self-contained and
portable. docs/superpowers/ (specs and plans) stays at the repo root.

Moved via cp+rm rather than git mv because directory rename() fails with
EPERM on this WSL /mnt DrvFs mount; git rename-detection pairs the
identical-content files at commit time.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

plugins/document-navigator/docs/api-stack/api/api-2pc/src/testing/conformance.md

@@ -0,0 +1,100 @@
+# `testing/`
+
+<!-- begin:auto-docs -->
+_(no submodules)_
+<!-- end:auto-docs -->
+
+## Purpose
+
+Provides `run2pcParticipantConformance(factory)` — a runnable test
+suite that pins the contract every 2PC writer participant MUST honour.
+Adapter authors drop a single import + invocation into a
+`tests/conformance/run-2pc-participant.test.ts` file in their package;
+the harness handles the rest.
+
+Shipping the harness on this package's `./testing` subpath keeps
+participants accountable to the same prepare/commit/rollback semantics
+the coordinator depends on at runtime. Without this harness, drift
+between participant implementations would only surface during
+integration testing — too late.
+
+## Features
+
+- Six pinned invariants (engine identifier, voter mode, prepare-then-
+  prepare-SQL, commit-prepared, rollback-prepared, idempotency-on-
+  second-rollback).
+- Per-scenario factory: every test starts from a fresh participant +
+  teardown so the suite is isolation-safe under parallel runs.
+- Uses `@suaveplan/testing/runner` — works under both Vitest and
+  Bun:test without re-importing.
+- Generates unique gids per scenario so re-runs do not collide.
+
+## Usage: Basic
+
+```ts
+// In an adapter package's tests/conformance/run-2pc-participant.test.ts
+import { run2pcParticipantConformance } from "@suaveplan/api-2pc/testing";
+import { createMyParticipant, teardownMyParticipant } from "../helpers";
+
+run2pcParticipantConformance({
+    async create() {
+        const participant = await createMyParticipant();
+        return {
+            participant,
+            teardown: () => teardownMyParticipant(participant),
+        };
+    },
+});
+```
+
+## Usage: Advanced
+
+The harness exposes no surface beyond `run2pcParticipantConformance` —
+deliberately. Adapter-specific assertions belong in adapter test
+files, not in the conformance harness. If your adapter needs to
+exercise behaviour the suite does not cover (e.g. cancellation,
+custom serialization), add a sibling test file:
+
+```ts
+import { describe, it } from "@suaveplan/testing/runner";
+import { run2pcParticipantConformance } from "@suaveplan/api-2pc/testing";
+
+describe("my-participant", () => {
+    run2pcParticipantConformance({ create: createMyParticipant });
+
+    it("cancels a stuck prepare on signal abort", { timeout: 30_000 }, async () => {
+        // adapter-specific assertion
+    });
+});
+```
+
+## API Reference
+
+- `interface TwoPcParticipantFactory`
+  - `create(): Promise<{ participant: RegisteredTwoPcParticipant; teardown: () => Promise<void> }>`
+- `function run2pcParticipantConformance(factory): void`
+  - Registers six `describe`/`it` blocks against the surrounding
+    runner. Returns nothing.
+
+## Implementation Notes
+
+The harness deliberately does NOT use a shared Postgres connection
+across scenarios. Each scenario calls `factory.create()` to get a
+fresh participant; the factory is expected to wire its own connection
+(directly to a Postgres container, against a shared pool, or against
+an `env-bridge` passthrough URL). This isolation prevents one
+scenario's leftover prepared transactions from contaminating the
+next.
+
+Gids embed `Date.now()` + a random suffix so re-runs within the same
+millisecond never collide on the underlying `pg_prepared_xacts`
+table. The cleanup `ROLLBACK PREPARED` at the end of the
+prepare-only scenario is best-effort: failure to roll back leaves
+the gid prepared until the next teardown sweep, but the harness's
+own teardown handle is the primary cleanup path.
+
+The harness is intentionally NOT exported from the package root (`./`
+subpath) — only `./testing`. This mirrors the convention used by
+sibling packages (`@suaveplan/i18n-shared/testing`,
+`@suaveplan/api-host/testing`) so production code can not accidentally
+depend on test-only symbols.