Setup repo: migrate architecture specs, code stubs, and tasks from alkhub_ts

Copy architecture docs, ADRs, storage domain specs, research, reviews,
and 56 storage architecture tasks from the alkhub_ts monorepo. Adapt for
standalone @alkdev/hub repo structure (src/ not packages/hub/).

Sanitize all sensitive information:
- Replace private IPs (10.0.0.1) with localhost defaults
- Remove internal server hostnames (dev1, ns528096)
- Replace /workspace/ private paths with npm package references
- Remove hardcoded credentials from examples
- Rewrite infrastructure.md without private network details

Add Deno project scaffolding: deno.json (pinned deps), .gitignore,
AGENTS.md, entry point. Migrate existing code stubs (crypto, config
types, logger) with updated import paths.

tasks/architecture/storage/specify-task-body-append-concurrency.md

@@ -0,0 +1,37 @@
+---
+id: specify-task-body-append-concurrency
+name: Specify concurrency model for hub.task.addNote
+status: completed
+depends_on: []
+scope: single
+risk: high
+impact: component
+level: implementation
+---
+
+## Description
+
+`hub.task.addNote` appends a timestamped note section to `body`. In a multi-agent system, read-modify-write is a race condition: Agent A reads body, Agent B reads body, both append, Agent A writes, Agent B overwrites A's addition.
+
+The review recommends specifying: `hub.task.addNote` must use DB-level concatenation (`UPDATE tasks SET body = body || $note WHERE id = $taskId`), not a read-modify-write cycle. Or use optimistic locking with `updatedAt`.
+
+## Acceptance Criteria
+
+- [ ] `tasks.md` specifies the concurrency model for `hub.task.addNote` explicitly
+- [ ] The recommended approach is DB-level concatenation: `UPDATE tasks SET body = body || $note WHERE id = $taskId`
+- [ ] If optimistic locking is offered as an alternative, it is documented with the `updatedAt` check pattern
+- [ ] The spec notes that the append-only approach (no read-modify-write) eliminates the race condition
+- [ ] A note on `body` being nullable is addressed: `COALESCE(body, '') || $note`
+
+## References
+
+- docs/reviews/storage-architecture-review-2026-04-21.md#C08
+- docs/architecture/storage/tasks.md:249-266
+
+## Notes
+
+> To be filled by implementation agent
+
+## Summary
+
+> To be filled on completion