docs(architecture): add ADR-022, resolve OQ-23 — handler registration, provenance, and composition authority

ADR-022 wires the three controls ADR-015 specified but left without
registration paths (C1-C4 from review #001): composition authority,
scoped env, and capabilities now enter through a HandlerRegistration
bundle. Provenance (Local, FromOpenAPI, FromMCP, FromCall, Session)
determines which ops can compose — leaves don't get composition
authority. CompositionAuthority replaces handler_identity: Identity
(it's a declared authority bundle, not a peer identity). Capabilities
are per-request from the bundle (resolves closure-capture vs context
ambiguity). Kernel/user analogy: user's authority checked at External
gate; handler's composition authority used inside; scoped env bounds
reachability.

Also fixes W1 (stale ADR-020 path example) and W3 (from_mcp missing
from adapter lists in operation-registry.md).

Spec updates: operation-registry.md (OperationRegistry,
HandlerRegistration, OperationContext, OperationEnv, registration
example, capability injection), call-protocol.md (build_root_context),
README.md, overview.md, open-questions.md (OQ-23), call/README.md.

docs/architecture/overview.md

@@ -1,6 +1,6 @@
 ---
 status: draft
-last_updated: 2026-06-19
+last_updated: 2026-06-20
 ---
 
 # Alknet Overview
@@ -212,6 +212,7 @@ All design decisions are documented as ADRs in [decisions/](decisions/).
 | [019](decisions/019-vault-assembly-layer-only.md) | Vault Assembly-Layer-Only Access | The assembly layer (CLI binary) is the sole direct caller; handlers never hold a vault reference |
 | [020](decisions/020-hd-derivation-for-encryption-keys.md) | HD Derivation for Encryption Keys | SLIP-0010 derivation from seed, not PBKDF2; salt field unused in v2 |
 | [021](decisions/021-key-rotation-via-version-indexed-paths.md) | Key Rotation via Version-Indexed Paths | Version-indexed derivation paths; `rotate` re-encrypts between versions |
+| [022](decisions/022-handler-registration-provenance-and-composition-authority.md) | Handler Registration, Provenance, and Composition Authority | Registration bundle carries provenance, composition authority, scoped env, capabilities; dispatch path reads from bundle |
 
 ## Open Questions