docs: add metagraph-module and forward-look architecture specs, remove SchemaBuilder legacy support

Graph type definitions as TypeBox Modules — the core architecture evolution
for @alkdev/storage. The SchemaBuilder is removed (no existing consumers),
replaced by direct TypeModule construction with Metagraph.Import() for
base attribute composition and Type.Composite() for node/edge type
specialization.

Key additions:
- metagraph-module.md: Module pattern, edge constraints as named entries,
  SchemaBuilder equivalence, DB bridge contracts (moduleToDbSchema return
  type, validateNode/validateEdge signatures), 10 design decisions (DD1-DD10)
- forward-look.md: pointer abstraction (ujsx ValuePointer analogy, JPATH
  Module), dbtype table rendering relationship, ujsx as universal IR pipeline

Critical corrections from architecture review:
- Type.Composite uses IntersectEvaluated (intersection, not Object.assign
  override) — overlapping keys with subtype relationships resolve correctly
- Type.Ref inside Type.Composite within a Module is verified working
- BaseNode/BaseEdge use Metagraph.Import() for same-package Modules (Option B),
  not local re-declaration (no circular dep within same package)
- Edge constraints use Type.String() for node type name arrays (not Type.Ref) —
  constraints contain names, not schemas

docs/architecture/overview.md

@@ -29,7 +29,7 @@ ecosystem.
 @alkdev/storage/
 ├── mod.ts                   → re-exports graphs/ (zero db deps)
 ├── src/
-│   ├── graphs/              → schema types + SchemaBuilder (no db deps)
+│   ├── graphs/              → Metagraph Module, bridge functions (no db deps)
 │   ├── sqlite/              → SQLite host (drizzle-orm/libsql)
 │   │   ├── tables/          → drizzle table definitions
 │   │   ├── relations.ts     → drizzle relational mappings
@@ -85,12 +85,16 @@ type with specific node types (operation call, subcall) and edge types
 This trades some query convenience for generality. Domain-specific queries are
 built on top of the graph query layer, not baked into table schemas.
 
-### D3: SchemaBuilder as the primary API surface
+### D3: Type.Module as the primary API surface
 
-The `SchemaBuilder` fluent API is the intended way to construct graph type
-definitions. It validates against TypeBox schemas at build time, ensuring that
-graph/node/edge type definitions are structurally sound before they're persisted
-to the database.
+The `Type.Module()` construction API is the intended way to define graph type
+definitions. The `Metagraph` Module provides base entries (`BaseNode`,
+`BaseEdge`, `Config`); concrete graph types compose them via `Metagraph.Import()`
+and `Type.Composite()`. The `SchemaBuilder` is removed.
+
+This replaces the earlier fluent builder pattern. The Module format provides
+native `Type.Ref()` for internal references, `Module.Import()` for cross-package
+references, and JSON Schema `$defs` that map directly to DB storage.
 
 ### D4: Injectable clients, no module-level side effects
 
@@ -147,7 +151,7 @@ consumed by the hub and spokes, not by storage itself.
 
 ### Implemented
 
-- Graph schema types and SchemaBuilder
+- Graph schema types and Metagraph Module (replaces SchemaBuilder)
 - SQLite host: 6 metagraph tables + actors table + Drizzle relations + client
   factory
 - TypeBox select/insert schemas generated from Drizzle tables (drizzlebox)
@@ -296,6 +300,8 @@ storage node attributes and operations call events), they should either:
 
 ## References
 
+- Metagraph Module evolution: [metagraph-module.md](./metagraph-module.md)
+- Forward-looking connections: [forward-look.md](./forward-look.md)
 - Operations architecture: `/workspace/@alkdev/operations/docs/architecture/README.md`
 - Pubsub architecture: `/workspace/@alkdev/pubsub/docs/architecture/README.md`
 - Flowgraph architecture: `/workspace/@alkdev/flowgraph/docs/architecture/README.md`