feat(call): remote_safe field on HandlerRegistration (ADR-028)

Adds the v1 data shape for peer-scoped default-deny registry filtering,
the one-way-door piece of the call-completion batch (ADR-028):

- HandlerRegistration gains pub remote_safe: bool, defaulting false across
  all provenance (Local, Session, FromOpenAPI, FromMCP, FromCall,
  FromJsonSchema) per ADR-028 §4. HandlerRegistration::new() keeps its
  existing 6-arg signature (defaults remote_safe: false), so all current
  call sites compile unchanged.
- Chainable HandlerRegistration::remote_safe(bool) setter + a
  OperationRegistryBuilder::remote_safe() helper that marks the
  most-recently-registered op (tracked via last_name, not HashMap
  iteration order which is unspecified).
- Field is data-only here — the filtering behavior (dispatch path +
  services/list hide) is wired in call/client/call-client, not this task.
  services/list is unchanged.
- Tests: default false, setter flips field, all six provenance variants
  default false, builder setter marks last op, existing call sites
  unchanged. 178 tests pass, clippy clean.

Refs: tasks/call/registry/remote-safe-marking.md
Refs: docs/architecture/decisions/028-callclient-peer-scoped-registry-filtering.md

tasks/call/registry/remote-safe-marking.md

@@ -1,7 +1,7 @@
 ---
 id: call/registry/remote-safe-marking
 name: Add remote_safe field to HandlerRegistration for CallClient peer-scoped filtering (ADR-028)
-status: pending
+status: completed
 depends_on: []
 scope: narrow
 risk: medium