feat: P2.5-5/6 add --peers/--ca-cert parsing to worker+scheduler with validation

Worker (P2.5-5):
- Added parse_peers() static helper to src/worker/src/main.c
- Switched getopt to getopt_long to support --peers and --ca-cert long options
- When --peers is given: parses into xce_cluster_config_t, calls
  xce_cluster_config_validate(), logs INFO with candidate count/identity/ca_cert
- If validation fails: prints clear error and exits(1)
- WARN logged when candidates_count > 3
- Backward compatible: no --peers falls back to existing single-controller path

Scheduler (P2.5-6):
- Added parse_peers() static helper to src/scheduler/src/main.c
- Extended argp struct with --peers (-P) and --ca-cert (-C) options
- Same validation/logging pattern as worker
- Backward compatible: no --peers falls back to existing single-controller path

Tests (new):
- src/lib/testsuite/test_cluster_parse.c: 8 unit tests for parse_peers logic
  (single entry, multiple entries, no-name format, empty/null/missing-port errors,
  name-stripped correctly, MAX_HA_CANDIDATES cap respected)
- Registered in test.c and meson.build
- All 8 tests GREEN; 3 pre-existing failures in unrelated GC/CSE tests unchanged

src/lib/meson.build

@@ -168,6 +168,7 @@ libxce_test_src = ['testsuite/test.c',
                    'testsuite/test_kvmgr_capture.c',
                    'testsuite/test_hooks.c',
                    'testsuite/test_cluster.c',
+                   'testsuite/test_cluster_parse.c',
                   ]
 
 libxce_test_deps = [libxce_deps, librtti_dep, unity_dep, libxce_dep]