feat(raft-apply-decoupling): build apply_committed_entry single dispatch seam (task 2.2)

Add apply_committed_entry(persist_t*, wal_type, lsn, payload, len) in
persist.c/persist.h as the single seam that turns a committed WAL
entry into an in-memory mutation plus its post-mutation notification
hook, covering job submit, job-state facts, queue control, and
worker control. Job-state facts route through 2.1's guard-only
apply_job_update_transition() core and fire a generic
HOOK_DETAIL_JOB_UPDATE, not per-type hooks — the wire format
(wal_jobstate_t {jobid, state}) cannot supply what the type-specific
cores/hooks require. This is a real, documented deviation from
design.md's per-type dispatch wording; tasks.md's Implementation
Notes flags it as unresolved and blocking for whoever wires this
into a live path (4.1/6.2/6.3).

Not yet wired into any live call site (replay wiring is 2.3).

src/controller/testsuite/controller_test.c

@@ -78,6 +78,7 @@ extern void test_ha_core_safety(void);
 extern void test_ha_partition(void);
 extern void test_persist_snapshot_entities(void);
 extern void test_apply_seam(void);
+extern void test_apply_committed_entry(void);
 
 void setUp(void) { return; }
 
@@ -225,6 +226,7 @@ int main(int argc, char* argv[])
     TEST(test_ha_partition);
     TEST(test_persist_snapshot_entities);
     TEST(test_apply_seam);
+    TEST(test_apply_committed_entry);
 
     return UNITY_END();
 }