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.

docs/decisions/ADR-002-jsonb-nullability-rationale.md

@@ -0,0 +1,17 @@
+# ADR-002: JSONB nullability rationale
+
+- **Status**: Accepted
+- **Date**: 2026-04-19
+- **Deciders**: alkdev
+
+## Context
+
+Some JSONB columns are NOT NULL (messages.data, parts.data, operations.inputSchema) while others are nullable (sessions.data, spokes.hostInfo, operations.outputSchema). Need a consistent rationale for when JSONB should be nullable.
+
+## Decision
+
+JSONB columns are NOT NULL when data is required for the record to be meaningful — a message without role-specific metadata or a part without type-specific content is incomplete. Nullable JSONB columns are for optional, evolving, or context-dependent data.
+
+## Consequences
+
+Minimal — this is a convention that matches the semantic meaning of each column. Positive: consistent mental model for schema design. Negative: none significant.