daemon: event.* fan-out (D5) + category.list/queue.list (D3) — GUI-ready

The two items aimed at pointing GUI at a real veloxd instead of mockd.

rpc/event_hub — per-subscription fan-out shared by both transports.
subscribe() registers a connection with no interest; set_filter()
(session.subscribe, replaces not adds) turns on event kinds and an
optional per-task id filter; publish() delivers a pre-built
notification to every matching subscriber. session.subscribe on both
UdsServer and WsServer now does the real thing — registers/updates a
subscription, tears it down in close_conn.

sched/scheduler — the on_engine_state hook now actually publishes:
- transition() is the one place a task's row changes state; it reads
  the store's own prior row for previousState (authoritative
  regardless of engine/scheduler timing), writes the error columns,
  and — when a hub is supplied — publishes event.task.state with
  {taskId, state, previousState, summary, error}. Wired into every
  transition: scheduler-driven (admission -> probing, resume ->
  connecting, pause) and engine-reported (on_engine_state).
- progress_snapshot(): one row per task the engine is tracking
  (EnginePort::progress(), a new interface method backed by
  DownloadHandle::progress()), plus a store side-effect
  (Tasks::update_progress) so download.list/get stay current between
  state transitions. Returns rows; does NOT publish itself — batching
  into one array message is the caller's job, per the schema's
  x-maxRateHz: 4 and AGENT-DAEMON.md item 5 ("one message per task per
  tick burns a core"). main.cpp's 250 ms timerfd is that caller: one
  event.task.progress per tick, only when there's something to say.

dispatcher::on_download_add now publishes event.task.added (schema:
"summary is always present so a client can insert the row without a
follow-up download.get").

store/categories, store/queues — the two D3 handlers GUI's panels
call. category.list projects the six seeded built-ins; queue.list
derives taskIds from tasks.queue_id/queue_position (Queue's own schema
note: a queue's stored row never carries membership, download.update
/ queue.reorder do).

Verified live end to end against tools/testserver: a subscribed client
sees event.task.added on add, then the full event.task.state sequence
(queued -> probing -> connecting -> downloading -> assembling ->
verifying -> complete) with correct previousState at every step, and
real category.list / queue.list results.

Tests: event_hub (filter-by-kind, filter-by-task-id, replace-not-add,
unsubscribe), store_categories_queues, plus new sched_scheduler cases
for event.task.state publishing and progress_snapshot's store
side-effect. 38 daemon/cli tests green; sched_scheduler / event_hub /
ws_server / uds_roundtrip TSan-clean.

deferrals.md: D5 mostly closed (event.task.removed and the
still-unpublished events wait on their owning D3 handlers); D3 down to
the remaining download.* verbs, rules/settings/limiter/schedule,
queue mutation, category mutation, grabber, media.

Co-Authored-By: Claude Sonnet 5 <[email protected]>
Claude-Session: https://claude.ai/code/session_01Upd9WhG9oppieig5nRDLig

daemon/src/rpc/uds_server.hpp

@@ -13,12 +13,14 @@
 #include <cstdint>
 #include <memory>
 #include <string>
+#include <optional>
 #include <system_error>
 #include <unordered_map>
 #include <vector>
 
 #include <nlohmann/json_fwd.hpp>
 
+#include "rpc/event_hub.hpp"
 #include "rpc/ndjson.hpp"
 #include "velox_proto.hpp"
 
@@ -28,7 +30,8 @@ class EventLoop;
 
 class UdsServer {
 public:
-    UdsServer(EventLoop& loop, velox::proto::Dispatcher& dispatcher, std::string socket_path);
+    UdsServer(EventLoop& loop, velox::proto::Dispatcher& dispatcher, EventHub& hub,
+             std::string socket_path);
     ~UdsServer();
 
     UdsServer(const UdsServer&) = delete;
@@ -51,6 +54,7 @@ private:
         bool close_after_flush = false;
         bool hello_ok = false;
         std::string session_id;
+        std::optional<EventHub::SubId> sub_id;
     };
 
     void on_listener_readable();
@@ -68,6 +72,7 @@ private:
 
     EventLoop& loop_;
     velox::proto::Dispatcher& dispatcher_;
+    EventHub& hub_;
     std::string path_;
     int listen_fd_ = -1;
     bool bound_ = false;   // path_ is ours to unlink on destruction