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/document-mappings-task-denorm-invariant.md

@@ -0,0 +1,38 @@
+---
+id: document-mappings-task-denorm-invariant
+name: Document mappings.task denormalization sync strategy
+status: completed
+depends_on: []
+scope: narrow
+risk: medium
+impact: component
+level: implementation
+---
+
+## Description
+
+The `mappings` table has both `taskId` (FK → tasks.id) and `task` (denormalized display name). No mechanism keeps them in sync. If `taskId` points to a task whose `slug` or `name` changes, `mappings.task` becomes stale. When `taskId` is SET NULL (task deleted), what happens to `task`?
+
+The review recommends documenting the invariant: "`mappings.task` is set to `tasks.slug` at insert time and is **not** automatically updated when the task's slug changes. When `taskId` is SET NULL (task deleted), `task` should also be SET NULL. This is a cache, not a source of truth." Alternatively, remove the denormalized column and use a VIEW that joins.
+
+## Acceptance Criteria
+
+- [ ] `coordination.md` documents the invariant for `mappings.task`: it is a cache of `tasks.slug`, set at insert time, not auto-updated
+- [ ] The behavior when `taskId` is SET NULL is documented: `task` should also be SET NULL (application-level or trigger)
+- [ ] If keeping the column: add a note that stale `task` values are acceptable (cache semantics)
+- [ ] If removing the column: replace with a VIEW definition and update coordination.md
+- [ ] `tasks.md:209` reference to `mappings.task` is updated to be consistent
+
+## References
+
+- docs/reviews/storage-architecture-review-2026-04-21.md#C06
+- docs/architecture/storage/coordination.md:22
+- docs/architecture/storage/tasks.md:209
+
+## Notes
+
+> To be filled by implementation agent
+
+## Summary
+
+> To be filled on completion