ADR-006: Unify on registry.execute() as the single invocation entry point.
Call protocol becomes internal transport for cross-process routing.
CallHandler calls execute() instead of reimplementing lookup/validation.
Access control enforcement in execute() with trusted flag for nested calls.
Default-deny: reject when requiredScopes non-empty and identity absent.
Source-vs-spec drift tables added to call-protocol.md and api-surface.md,
documenting all gaps between architecture docs and current source:
- ADR-005 gaps (envelope types, pipeline, factory functions)
- ADR-006 gaps (unified invocation, access control, CallHandler refactor)
- Two bugs: checkAccess() resource bypass when identity.resources is
undefined, and PendingRequestMap type/class naming conflict