docs: restructure architecture docs to flowgraph pattern

- Create decisions/ directory with 32 numbered ADRs (ADR-001 through ADR-032)
  extracted from inline DD/SD/ED/SE decision sections
- Create open-questions.md with 16 OQs organized by theme, cross-referenced
  to ADRs, with status tracking (resolved/open)
- Create README.md as architecture index with doc table, ADR table, and
  lifecycle status definitions (draft/reviewed/stable/deprecated)
- Replace inline decision sections in all spec docs with ADR reference tables
- Replace inline open questions with OQ references to centralized tracker
- Update frontmatter: metagraph-module.md, overview.md, sqlite-host.md → reviewed;
  schema-evolution.md and encrypted-data.md remain draft
- DD1-DD10 → ADR-009 through ADR-018
- D1-D8 → ADR-001 through ADR-008
- SD1-SD5 → ADR-019 through ADR-023 (SD5 folded into ADR-006/008)
- ED1-ED5 → ADR-023 through ADR-027
- SE1-SE5 → ADR-028 through ADR-032

docs/architecture/decisions/001-deno-first-jsr-publishes.md

@@ -0,0 +1,24 @@
+# ADR-001: Deno-first, JSR publishes, npm comes free
+
+## Status
+
+Accepted
+
+## Context
+
+The package needs to be usable from both Deno and Node.js. Maintaining separate build pipelines (dnt, esbuild) is overhead. JSR automatically provides npm compatibility via `@jsr/alkdev__storage`.
+
+## Decision
+
+Publish to JSR (`deno publish`). npm compatibility is automatic via JSR's npm layer. No separate dnt build step.
+
+## Consequences
+
+- Source files use `.ts` extension with explicit import paths (Deno convention)
+- `--allow-slow-types` is used on publish; `"exclude": ["no-slow-types"]` in lint config
+- npm consumers install `@jsr/alkdev__storage`
+- No dual-publishing pipeline to maintain
+
+## References
+
+- [overview.md](../overview.md)