fix: port main fixes stranded by the v2 rewrite (round 2)

Native subagent observability (#5219), wired per its spec's v2 merge plan:
- getWorkflowScript RPC re-homed onto the v2 WS surface (contracts, rpc
  group, ws handler, auth scope, client atom).
- AgentsPanel fed by the spec's mapper swap: projectedSubagentsToRuntime
  maps orchestration-v2 subagent entities into the panel model;
  deriveAgentPanelModel's v2Projection leg is now live and the v1 fold
  never runs. Agents surface wired into ChatView + RightPanelTabs.
Other ports and reconciliations:
- Shell reconnect-loop fix (#5561) ported into the v2 shell sync
  (same-session resubscribes resume from the in-memory cursor), with the
  cursor-resume regression test adapted to v2 fixtures.
- Mobile end-follow latch (#5566) ported onto the v2 ThreadFeed.
- Claude ede_diagnostic interrupt classification (#5557) ported into
  ClaudeAdapterV2 (aborted_tools/aborted_streaming => interrupted; CLI
  telemetry never becomes the failure banner). #5559 needs no v2 port
  (unknown system subtypes are already ignored).
- Plan sidebar removed from the v2 ChatView/ChatComposer per main's
  plans-fold-into-chat rework (#5558); rightPanelStore stays at main's
  surface set.
- SettingsPanels rebuilt as main's refactored version plus the branch's
  composer-context setting; sidebar snooze respects the time format
  (#4438 follow-through).
- v1-only leftovers deleted: zombie v1 adapters/ingestion/tests the v2
  rewrite removes, the v1-bound transfer-budget CI harness (#5350, needs
  a v2 rebuild), and main's v1 client pagination machinery (#5493 client
  side; the 037 keyset migration is kept — server-side v2 windowing is a
  follow-up).

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

Author: juliusmarminge