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/validation.md

@@ -325,11 +325,11 @@ not validation.
 
 ## References
 
-- `docs/research/alknet-typedef/findings.md` §"Validation" — the POC's
-  custom keyword validators for all 17 kinds
+- `@alkdev/alknet: docs/research/alknet-typedef/findings.md`
+  §"Validation" — the POC's custom keyword validators for all 17 kinds
 - [ADR-004](decisions/004-error-handling-validation-strategy.md) —
   error handling and validation strategy
-- [schema-layer.md](schema-layer.md) — the 17 AlkType kinds that the
+- [schema-layer.md](schema-layer.md) — the 19 AlkType kinds that the
   validators check
 - [data-access.md](data-access.md) — read/write functions that operate
   on the same buffers