feat(worker-rejoin-resync): task 4.3 - wire query receipt and post-join gate

Add OPCode_jobStateQuery dispatch to myreq_handler with multi-page query
reassembly, routing to task 4.2's xcecd_resync_answer_query() (Req
8.1, 8.3). Gate the worker's resumption of normal post-join operation
on a resync_pending flag until the full report has sent (Req 3.8).

Fixes bug-1749 (xcecd_resync.c was never added to the worker's
production source lists - task 4.2's build only ever exercised it via
the test binary's white-box include).

Round 1 review caught bug-1750: the gate sat as checking_connection()'s
entry guard, so a connection drop mid multi-page query left
resync_pending stuck forever, permanently disabling the worker's only
reconnect mechanism (Req 6.1 violation). Round 2 narrows the gate to
guard only the rejoin action, and resets it from xcecd_on_reconnect()
so a stalled query can never wedge it past one reconnect cycle.

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01Y4M5MJM2zK6nU43da267Ku

src/worker/meson.build

@@ -7,6 +7,7 @@ xcecd_worker_srcs = [
   'src/static_array.c',
   'src/xcecd_cgroups.c',
   'src/xcecd_worker_utils.c',
+  'src/xcecd_resync.c',
   'src/controller_connector.c',
   'src/xcecd_dbus_manager.c',
   'src/xcecd_db.c',
@@ -84,6 +85,7 @@ xcecd_srcs = [
   'src/controller_connector.c',
   'src/resource_sync.c',
   'src/xcecd_worker_utils.c',
+  'src/xcecd_resync.c',
   'src/hardware_monitor.c',
   'src/node_information.c',
   'src/job_information.c'