Clean up rebranding drift in docs, agent configs, and source comments

Fix stale references left over from the alknet-typedef → alktype migration:
- .opencode/agents/: replace @alkdev/alknet constraints (tokio, crypto, feature
  flags, anyhow/thiserror) with alktype-accurate ones (sync, AlkTypeError,
  WASM-clean); fix @alkimiadev → @alkdev org name; remove nonexistent AGENTS.md
  ref; replace alknet-http/alknet-agent spec examples
- docs/sdd_process.md: fix wrong package name (@alkdev/storage → @alkdev/alktype)
- docs/architecture/: rewrite dangling /workspace/ and docs/research/ paths as
  @alkdev/alknet: cross-repo references with explanatory notes; fix
  @alkimiadev → @alkdev; fix 'not yet used by any alknet crate' stale context
- src/ + tests/: correct '17 AlkType kinds' → '19' in doc comments (enum has 19
  variants; pre-existing count error); fix dangling /workspace/ path in
  poc_roundtrip.rs

docs/architecture/layout-engine.md

@@ -348,13 +348,14 @@ See [open-questions.md](open-questions.md) for full details.
 
 ## References
 
-- `docs/research/alknet-typedef/findings.md` §"POC Results" — POC 1
-  (aligned OffsetMap) and POC 2 (packed LayoutBuilder/SequentialReader)
+- `@alkdev/alknet: docs/research/alknet-typedef/findings.md` §"POC Results"
+  — POC 1 (aligned OffsetMap) and POC 2 (packed
+  LayoutBuilder/SequentialReader)
 - [ADR-002](decisions/002-two-layout-modes-packed-vs-aligned.md) —
   the two layout modes decision
 - [ADR-003](decisions/003-schema-annotations.md) — schema
   annotations
-- [schema-layer.md](schema-layer.md) — the 17 AlkType kinds and their
+- [schema-layer.md](schema-layer.md) — the 19 AlkType kinds and their
   byte sizes
 - [data-access.md](data-access.md) — read/write functions that use the
   computed offsets