hive-c0re: serialise the matrix and knowledge sweeps through the job queue

The matrix sweep and the /knowledge pull each had concurrent callers
(#4723 item 4). Two overlapping knowledge pulls fail on .git/index.lock
and the remote-tracking ref lock: 30 of 30 concurrent replays of the
reset/clean/pull sequence in a scratch repo errored, 0 of 10 sequential
ones did. Two overlapping matrix sweeps on a hive with no persisted
Space / chat-room id both miss the by-name lookup and both createRoom
(from reading the code, not reproduced against a homeserver). On every
boot the MatrixSweep DAG node and the main.rs loop's immediate first
call ran at once.

Every sweep now runs as a job node, and each sweep's node holds its own
capacity-1 queue resource (Resource::MatrixSweep,
Resource::KnowledgeTree), the MetaWindow pattern: the scheduler never
starts a second pass of one sweep while the first holds the resource,
and different sweeps still run side by side.

- templates::matrix_sweep / templates::knowledge_pull build the node
  with its resource; boot, the periodic loops and the swarm event all
  use them.
- JobQueue::insert_unless_live folds a submission into a live node of
  the same kind instead of queueing another. Periodic ticks fold into a
  queued or running pass. The swarm knowledge event folds into a queued
  pull only, and queues one behind a running pull, which may have
  fetched before the push.
- The main.rs matrix loop no longer sweeps immediately at startup; the
  boot MatrixSweep node is the startup pass, as KnowledgePull already
  was for knowledge.
- The executors bound each pass (10 min matrix, 5 min knowledge), since
  a hung pass would otherwise hold its resource against every later one,
  and own the sweep-health banners, so every pass reports to them.

Replaces the SweepLock version of this branch, per review.

Refs #4723

hive-c0re/src/job_queue/model.rs

@@ -144,12 +144,13 @@ pub enum NodeKind {
     /// One-shot boot-time forge user/token sweep for every existing
     /// container (`forge::ensure_all`). Agentless.
     ForgeSweep,
-    /// One-shot boot-time matrix user/space sweep (`matrix::ensure_all`).
-    /// Agentless.
+    /// Matrix user/space sweep (`matrix::ensure_all`): at boot and every 30
+    /// minutes. Agentless.
     MatrixSweep,
     /// One-shot boot-time Forgejo webhook registration. Agentless.
     WebhookRegister,
-    /// One-shot boot-time `/knowledge` pull (`knowledge::pull`). Agentless.
+    /// `/knowledge` pull (`knowledge::pull`): at boot, on the swarm
+    /// knowledge-changed event, and hourly. Agentless.
     KnowledgePull,
     /// One-shot boot-time pull of the agent set the swarm controller
     /// declares for this hive (`wanted::pull`). Agentless.