T-129: event streaming over the socket — clide tail --events

Sixth slice of T-99. Long-lived event subscription path, the second
half of D-6.

Wire shape:
- Client sends `{cmd:"tail", args:{flags:{events:true, filter:X}}}`.
- Server responds with `{ok:true, data:{streaming:true, filter:X}}`.
- Server pushes `{type:"event", subsystem, kind, ts, data}` lines
  until the client closes.

Server (lib/src/ipc/server.dart):
- Takes a DaemonBus, subscribes to DaemonEvent on start.
- Per-subsystem ring buffer (replayDepth=16 per D-6) populated on
  every emit.
- `tail --events` connection: send ack, replay matching events from
  ring, register the client for future fanout.
- _argv envelope now unwrapped at the server layer so the streaming
  check sees the inner `tail` cmd (not just `_argv`).
- Broken subscriber writes drop the subscriber cleanly; the bus
  doesn't block on a stalled client.

Client (native/clide-cli/clide.c):
- Sniffs `data.streaming:true` in the ack. If set, loops reading
  JSON-line events to stdout (with fflush per line) until EOF.

Tests:
- test/ipc/server_streaming_test.dart — 8 cases covering ack shape,
  filter, replay buffer (size + ordering), multi-subscriber fanout,
  broken-subscriber cleanup.
- test/cli/clide_cli_e2e_test.dart gets a tail --events test that
  spawns the C client, emits two events on the bus, asserts they
  print on stdout.

T-99 children remaining: T-130 (MCP), T-131 (wrap-up).

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

.pql/changelog/ticket_history/2026-05.sql

@@ -1862,3 +1862,5 @@ INSERT INTO ticket_history (ticket_id, field, old_value, new_value, changed_by,
 INSERT INTO ticket_history (ticket_id, field, old_value, new_value, changed_by, changed_at, created_at, updated_at, deleted_at, hash, canonical_version) VALUES ('T-127', 'status', 'in_progress', 'done', NULL, '2026-05-19 10:03:26', '2026-05-19 10:03:26', '2026-05-19 10:03:26', NULL, 'b8bf877d2057f7baa5acf6af7a13d529', 1) ON CONFLICT(hash) DO NOTHING;
 INSERT INTO ticket_history (ticket_id, field, old_value, new_value, changed_by, changed_at, created_at, updated_at, deleted_at, hash, canonical_version) VALUES ('T-128', 'status', 'backlog', 'in_progress', NULL, '2026-05-19 10:05:09', '2026-05-19 10:05:09', '2026-05-19 10:05:09', NULL, '763a80ec25b5fe712e5ad44b75dbb22f', 1) ON CONFLICT(hash) DO NOTHING;
 INSERT INTO ticket_history (ticket_id, field, old_value, new_value, changed_by, changed_at, created_at, updated_at, deleted_at, hash, canonical_version) VALUES ('T-128', 'status', 'in_progress', 'done', NULL, '2026-05-19 10:06:46', '2026-05-19 10:06:46', '2026-05-19 10:06:46', NULL, 'cc53b46764f28515d735aa77c8eeef2c', 1) ON CONFLICT(hash) DO NOTHING;
+INSERT INTO ticket_history (ticket_id, field, old_value, new_value, changed_by, changed_at, created_at, updated_at, deleted_at, hash, canonical_version) VALUES ('T-129', 'status', 'backlog', 'in_progress', NULL, '2026-05-19 12:06:39', '2026-05-19 12:06:39', '2026-05-19 12:06:39', NULL, '575584f46d21b51bab3e69da1b940718', 1) ON CONFLICT(hash) DO NOTHING;
+INSERT INTO ticket_history (ticket_id, field, old_value, new_value, changed_by, changed_at, created_at, updated_at, deleted_at, hash, canonical_version) VALUES ('T-129', 'status', 'in_progress', 'done', NULL, '2026-05-19 12:19:51', '2026-05-19 12:19:51', '2026-05-19 12:19:51', NULL, 'e9bf50652357521c7ee74bd6577e8108', 1) ON CONFLICT(hash) DO NOTHING;

.pql/changelog/tickets/2026-05.sql

@@ -2156,3 +2156,14 @@ Acceptance:
 3. flutter analyze + full test suite green.
 
 Source: T-99 sketch. Depends on T-127.', 'done', 'medium', NULL, NULL, NULL, '2026-05-18 11:59:06', '2026-05-19 10:06:46', NULL, '481c51b17b027b5a04279a0ef6a3a029', 1) ON CONFLICT(id) DO UPDATE SET type=excluded.type, parent_id=excluded.parent_id, title=excluded.title, description=excluded.description, status=excluded.status, priority=excluded.priority, assigned_to=excluded.assigned_to, team=excluded.team, decision_ref=excluded.decision_ref, updated_at=excluded.updated_at, deleted_at=excluded.deleted_at, hash=excluded.hash, canonical_version=excluded.canonical_version WHERE excluded.updated_at > tickets.updated_at OR (excluded.updated_at = tickets.updated_at AND excluded.hash > tickets.hash);
+INSERT INTO tickets (id, type, parent_id, title, description, status, priority, assigned_to, team, decision_ref, created_at, updated_at, deleted_at, hash, canonical_version) VALUES ('T-129', 'task', 'T-99', 'event streaming over the socket — `clide tail --events`', 'Sixth slice of T-99(a). Long-lived subscription channel — the second half of D-6 (`clide tail --events [--filter <subsystem>[:<id>]]`).
+
+Client opens a connection, sends {"subscribe": "<subsystem>|*"}, server pushes JSON-line events until the client closes. Per D-6: replay buffer per subsystem (default depth 16) so a late subscriber still sees recent effects.
+
+Acceptance:
+1. `clide tail --events --filter git` streams git.* events from the running app.
+2. Replay buffer per subsystem; new subscribers receive the last 16 events.
+3. Server doesn''t block writes on a slow client (back-pressure handling per Q-2 — drop with a warning or apply flow control; resolve in this ticket).
+4. End-to-end smoke: launch app, run `clide tail --events --filter pane` in another shell, perform a pane action in the UI, observe the event.
+
+Source: T-99 sketch. Depends on T-124 + T-126.', 'done', 'medium', NULL, NULL, NULL, '2026-05-18 11:59:11', '2026-05-19 12:19:51', NULL, '44c9141fea8635a9c03053afa92f3999', 1) ON CONFLICT(id) DO UPDATE SET type=excluded.type, parent_id=excluded.parent_id, title=excluded.title, description=excluded.description, status=excluded.status, priority=excluded.priority, assigned_to=excluded.assigned_to, team=excluded.team, decision_ref=excluded.decision_ref, updated_at=excluded.updated_at, deleted_at=excluded.deleted_at, hash=excluded.hash, canonical_version=excluded.canonical_version WHERE excluded.updated_at > tickets.updated_at OR (excluded.updated_at = tickets.updated_at AND excluded.hash > tickets.hash);