docs(architecture): add ADR-014 secret material flow, remove vault ops from call protocol

Resolve the contradiction between ADR-008's "capability source" model
and operation-registry.md showing vault operations on the wire. ADR-014
establishes: vault is assembly-layer only, capabilities carry outbound
credentials (distinct from inbound identity), call protocol carries no
secret material, adapters take credential sources not static tokens.

- Add ADR-014 (Secret Material Flow and Capability Injection)
- Remove vault/derive, vault/unlock, vault/decrypt from call protocol
  registration examples and all spec examples
- Add Capabilities field to OperationContext, propagate through
  LocalOperationEnv nested calls
- Add Capability Injection section to operation-registry.md
- Add no-secret-material wire constraint to call-protocol.md
- Add streaming subscribe example (LLM chat with Vercel UI chunks)
- Add Security Model section to overview.md (identity vs capabilities)
- Trim WASM treatment from ~20 lines to a design-constraint note
- Add OQ-16 (resolved: no vault ops on wire), update OQ-08, OQ-15
- Update ADR-003, ADR-008, ADR-013 to remove stale "via call protocol"
  vault references

docs/architecture/README.md

@@ -1,15 +1,15 @@
 ---
 status: draft
-last_updated: 2026-06-17
+last_updated: 2026-06-18
 ---
 
 # Alknet Architecture
 
 ## Current State
 
-**Pre-implementation.** The project has completed a pivot from a three-layer model to an ALPN-as-service model. The greenfield workspace contains only `alknet-vault` (stable) and research/reference material. Foundational ADRs (001–013) are in place, including the BiStream type definition (ADR-007), vault integration (ADR-008), ALPN router/endpoint (ADR-010), AuthContext structure (ADR-011), call protocol stream model (ADR-012), and Rust as canonical implementation language (ADR-013). The alknet-core and alknet-call crate specs are in draft.
+**Pre-implementation.** The project has completed a pivot from a three-layer model to an ALPN-as-service model. The greenfield workspace contains only `alknet-vault` (stable) and research/reference material. Foundational ADRs (001–014) are in place, including the BiStream type definition (ADR-007), vault integration (ADR-008), ALPN router/endpoint (ADR-010), AuthContext structure (ADR-011), call protocol stream model (ADR-012), Rust as canonical implementation language (ADR-013), and secret material flow with capability injection (ADR-014). The alknet-core and alknet-call crate specs are in draft.
 
-**Next step**: Review alknet-call spec documents, then begin implementation. OQ-11 (handler-level auth resolution observability) will be resolved during implementation.
+**Next step**: Review alknet-call spec documents, then begin implementation. OQ-11 (handler-level auth resolution observability) and OQ-15 (call protocol client and adapter contract) will be resolved during implementation.
 
 ## Architecture Documents
 
@@ -23,8 +23,8 @@ last_updated: 2026-06-17
 | [crates/core/auth.md](crates/core/auth.md) | draft | AuthContext, Identity, IdentityProvider, AuthToken, resolution flow |
 | [crates/core/config.md](crates/core/config.md) | draft | StaticConfig, DynamicConfig, ArcSwap, ConfigReloadHandle |
 | [crates/call/README.md](crates/call/README.md) | draft | alknet-call crate index |
-| [crates/call/call-protocol.md](crates/call/call-protocol.md) | draft | CallAdapter, EventEnvelope framing, stream model, PendingRequestMap, bidirectional calls |
-| [crates/call/operation-registry.md](crates/call/operation-registry.md) | draft | OperationSpec, Handler, OperationRegistry, AccessControl, service discovery, irpc integration |
+| [crates/call/call-protocol.md](crates/call/call-protocol.md) | draft | CallAdapter, EventEnvelope framing, stream model, PendingRequestMap, bidirectional calls, streaming subscribe example |
+| [crates/call/operation-registry.md](crates/call/operation-registry.md) | draft | OperationSpec, Handler, OperationRegistry, AccessControl, capability injection, service discovery, irpc integration |
 
 ## ADR Table
 
@@ -43,6 +43,7 @@ last_updated: 2026-06-17
 | [011](decisions/011-authcontext-structure.md) | AuthContext Structure and Resolution Flow | Accepted |
 | [012](decisions/012-call-protocol-stream-model.md) | Call Protocol Stream Model | Accepted |
 | [013](decisions/013-rust-canonical-implementation.md) | Rust as Canonical Implementation Language | Accepted |
+| [014](decisions/014-secret-material-flow-and-capability-injection.md) | Secret Material Flow and Capability Injection | Accepted |
 
 ## Open Questions
 
@@ -54,7 +55,8 @@ See [open-questions.md](open-questions.md) for the full tracker.
 - **OQ-03**: ALPN naming — `alknet/` prefix, no version (ADR-006)
 - **OQ-05**: Multi-connectivity endpoint — quinn + iroh, both feature-gated (ADR-010)
 - **OQ-06**: ALPN per connection, not per stream (ADR-006)
-- **OQ-08**: Vault integration — CLI-embedded via call protocol (ADR-008)
+- **OQ-08**: Vault integration — CLI-embedded, assembly-layer only (ADR-008, ADR-014)
+- **OQ-16**: Safe vault operations for call protocol exposure — none for now (ADR-014)
 
 **Resolved two-way doors:**
 - **OQ-04**: Dynamic handler registration — static at startup (ADR-010)
@@ -67,7 +69,7 @@ See [open-questions.md](open-questions.md) for the full tracker.
 - **OQ-11**: Handler-level auth resolution observability — decide during implementation
 
 **Open one-way doors (need ADR before implementation):**
-- **OQ-15**: Call protocol client and adapter contract — alknet-call needs both the server (CallAdapter) and client (call invocation over QUIC), plus the adapter contract traits (from_*, to_*) that enable composition
+- **OQ-15**: Call protocol client and adapter contract — alknet-call needs both the server (CallAdapter) and client (call invocation over QUIC), plus the adapter contract traits (from_*, to_*) that enable composition. ADR-014 constrains the adapter contract: adapters take credential sources from the assembly layer, not static tokens.
 
 **Deferred (not active):**
 - **OQ-09**: WASM target boundaries — design constraint, not deliverable