docs: record module HTTP architecture

Phase 5B, pass 3: adds ADR 0015 recording the durable module HTTP
routing and production runtime lifecycle architecture pass 1 and pass
2 implemented, extending ADR 0006 and ADR 0014 without superseding
either. Adds narrow cross-reference notes to both, and to the ADR
index, pointing at ADR 0015 for the work they deferred, while
preserving their historical text and accepted status.

Corrects stale forward-looking "pass 2"/future-tense language left
over from pass 1 in core/src/modules/runtime.ts and
packages/contracts/src/module-http.ts (comment-only; production
behavior unchanged), and a shutdown-lifecycle description in
docs/development/testing.md that predated the module-runtime-stop
step pass 2 added between draining the HTTP server and closing the
pool.

Full audit against origin/main...HEAD found the architecture,
contract, startup ordering, routing, authorization/origin
enforcement, and PostgreSQL integration coverage from passes 1-2
sound; the one concrete defect found (Vary-header merge producing an
invalid "*, Origin, Cookie" combination and case-sensitive duplicate
tokens) was already fixed with focused regression tests in a separate
commit (bf76f4e), not amending either checkpoint commit.

Co-Authored-By: Claude Sonnet 5 <[email protected]>

docs/architecture/decisions/README.md

@@ -23,3 +23,4 @@ ADRs capture durable choices that affect more than one package or phase.
 - [0012: Production-equivalent identity origin/CSRF protection under test](0012-identity-origin-csrf-protection-under-test.md) — Accepted
 - [0013: Core authorization, permission registry, and platform-owner bootstrap](0013-core-authorization-and-owner-bootstrap.md) — Accepted
 - [0014: Module permission declarations and platform permission registry](0014-module-permission-declarations-and-platform-registry.md) — Accepted
+- [0015: Static module HTTP routing and production runtime lifecycle](0015-static-module-http-routing-and-runtime-lifecycle.md) — Accepted