docs(adr): add repository ADR index mirroring the wiki ADR-Index page

Adds docs/adr/README.md as the in-repo copy of the ADR index (§70 of the
wiki ADR-Index page), including the "ADR-006 | Kysely contained inside DB
adapter" entry, the §46 six-sections mandate, the §71 architectural fitness
tests and the §68 architecture review gates. Committed ADRs in docs/adr/
must record a decision that matches their §70 row; the wiki page remains
the canonical index.

docs/adr/README.md

@@ -0,0 +1,65 @@
+# ADR index (§70)
+
+Repository copy of the ADR index from the wiki ADR-Index page (§70): the
+canonical list of architectural decisions, committed or planned. Every ADR
+committed to `docs/adr/` must record a decision that matches its row in
+section 70; the wiki page remains the canonical index.
+
+| ADR | Decision |
+|---|---|
+| ADR-001 | Modular monolith |
+| ADR-002 | Node.js 24 LTS runtime |
+| ADR-003 | TypeScript 6.0.3 pending TS7.1 ecosystem review |
+| ADR-004 | Fastify 5 HTTP runtime |
+| ADR-005 | PostgreSQL 18 sole canonical DB |
+| ADR-006 | Kysely contained inside DB adapter |
+| ADR-007 | React SSR for public rendering |
+| ADR-008 | React/Vite admin |
+| ADR-009 | Zero-JS public baseline |
+| ADR-010 | Client-island model for optional public interactivity |
+| ADR-011 | JSON Schema + TypeBox + Ajv validation |
+| ADR-012 | EPPP Extension API hides framework internals |
+| ADR-013 | Node/Amber is a theme extension |
+| ADR-014 | Blog is a first-party content extension |
+| ADR-015 | Versioned block documents |
+| ADR-016 | Versioned page composition |
+| ADR-017 | Extension-owned migrations/tables |
+| ADR-018 | Docker Compose primary installation |
+| ADR-019 | Opaque DB-backed admin sessions |
+| ADR-020 | Separate anonymous preference identity |
+| ADR-021 | Local media storage through storage port |
+| ADR-022 | PostgreSQL jobs before external broker |
+| ADR-023 | No Redis initially |
+| ADR-024 | No microservices initially |
+| ADR-025 | Trusted build-time executable extensions in v1 |
+| ADR-026 | Exact dependency pinning + controlled upgrade lanes |
+| ADR-027 (v1.1) | `core.markdown` block restores Markdown authoring inside the block model |
+| ADR-028 (v1.1) | Hardened outbound fetch as a core service; extensions never fetch directly |
+| ADR-029 (v1.1) | Embed provider allowlist enforced in renderer and generated CSP |
+| ADR-030 (v1.1) | Native server-side SVG charts and diagrams with an accessibility contract |
+| ADR-031 (v1.1) | Theme renaming replaces trademark references |
+| ADR-032 (v1.1) | Day-one byte budgets; latency targets from measurement |
+
+Every ADR contains: Context, Decision, Alternatives, Consequences, Operational
+impact, Revisit trigger (§46 E01-S01).
+
+## Architectural fitness tests (§71)
+
+- **Add Ledger/Paper:** create `theme-paper` extension → register
+  manifest/tokens/assets → optionally override renderer slots → tests →
+  include in build. Failure = editing Home/Post domain, core DB, auth, or
+  `if (theme === "paper")` in core.
+- **Add Reading:** create `org.eppp.reading` → migrations → public route →
+  admin contribution → Home section → settings → job(s) → content/block
+  contributions. Failure = core learning seam/half-life/bookmark/link-health
+  semantics.
+
+## Architecture review gates (§68)
+
+Gate A (end Sprint 1): publish a real post without core becoming
+blog/Amber-specific. Gate B (end Sprint 3): add a Home feature as an extension
+with no core edits. Gate C (end Sprint 4): a radically different theme runs
+without changing content/business logic. Gate D (end Sprint 5): visitor
+preference persists without coupling to auth or theme storage. Gate E (before
+public SDK): Extension API v1 proven enough to maintain. Gate F (Reading):
+Reading owns its whole domain without `if (readingEnabled)` in core.