feat(shared-queues): materialized competing consumers + dispatcher branch (D3.2)

The consumption side of shared durable queues:
- Thread `shared` through BundleTrigger::Queue + QueueTriggerSpec + the
  trigger identity; validate_bundle_for requires a shared queue on a group
  to name a declared kind='queue' collection (a shared queue on an app is
  rejected by the existing app-owner shared guard).
- materialize: a shared queue template materializes a consumer per
  descendant (the M5 one-consumer-slot skip is bypassed for shared —
  competing consumers are intended; each descendant gets one copy).
- dispatcher: ActiveQueueConsumer gains shared_group (from the materialized
  copy's source template via LEFT JOIN); dispatch_one_queue +
  handle_queue_failure route claim/ack/nack/terminal to the group store
  when shared_group is Some, via q_claim/q_ack/q_nack/q_terminal helpers. A
  group claim is normalized to a ClaimedMessage under the consuming app so
  the handler path is unchanged; the reclaim task also drains the group
  store. Exhausted shared messages are dropped (no group dead-letter store
  yet — documented deferral).

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

crates/picloud-cli/src/cmds/pull.rs

@@ -220,6 +220,8 @@ pub async fn run(app_ident: &str, dir: &Path, force: bool, mode: OutputMode) ->
                     visibility_timeout_secs: Some(d.visibility_timeout_secs),
                     dispatch_mode,
                     retry_max_attempts,
+                    // app-owned triggers are never shared (group-only).
+                    shared: false,
                 });
             }
             // `email` is skipped: the server stores the sealed secret value,