feat(shared-triggers): visibility + tests + docs (M2.5)

- `shared` column in `pic triggers ls --group` (TriggerTemplateInfo + DTO +
  report + renderer).
- manager-core/tests/shared_triggers.rs: a shared write matches the group's
  shared trigger and NOT a same-named per-app trigger; a per-app write matches
  the app trigger and NOT the shared one (the `shared` flag is the boundary).
- shared_triggers journey: declarative authoring applies, ls --group shows
  shared, an undeclared-collection shared trigger + an app shared trigger are
  rejected.
- docs: §11.6 + CLAUDE.md move shared-collection triggers from Deferred to
  implemented.

Completes M2. (Pre-existing async-dispatcher timing flakes pass in isolation.)

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

crates/picloud-cli/tests/cli.rs

@@ -43,6 +43,7 @@ mod routes;
 mod scripts;
 mod sealed;
 mod secrets;
+mod shared_triggers;
 mod staleness;
 mod suppress;
 mod tree;