feat: add persist.h — WAL types, persist_config_t, slot_key_t (P0-B)

- Define wal_entry_hdr_t (40 bytes, _Static_assert enforced)
- Define wal_entry_type enum (WAL_JOB_SUBMIT=1 … WAL_CHECKPOINT=100)
- Define persist_config_t with persist_config_defaults() inline helper
- Define slot_key_t (index, key[XCE_MAXNAME_LEN], key_len)
- Forward-declare persist_t opaque struct and full persist_* API surface
- Bootstrap controller Unity test suite (controller_unit_test binary)
- Register test('controller test', …, suite: 'controller') in meson
- 4 new tests all PASS: wal_header_size, wal_entry_types,
  persist_config_defaults, slot_key_t_fields

src/controller/testsuite/controller_test.c

@@ -0,0 +1,86 @@
+#include <argp.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+
+#include <unity/unity.h>
+
+extern void test_persist_types(void);
+
+void setUp(void) { return; }
+
+void tearDown(void)
+{
+    printf("\n-----------------------------------------------------\n");
+    return;
+}
+
+static char doc[]      = "controller_test";
+static char args_doc[] = "";
+
+#define MAX_TESTS (256)
+
+struct arguments {
+    int   ntests;
+    char* tests[MAX_TESTS];
+};
+
+static struct argp_option options[] = {
+    { "run", 't', "STR", 0, "run test" },
+    { 0 }
+};
+
+static error_t parse_opt(int key, char* arg, struct argp_state* state)
+{
+    struct arguments* arguments = state->input;
+
+    switch (key) {
+    case 't':
+        if (arguments->ntests >= MAX_TESTS) {
+            fprintf(stderr, "Too many tests\n");
+            exit(-1);
+        }
+        arguments->tests[arguments->ntests] = arg;
+        arguments->ntests++;
+        break;
+    default:
+        return ARGP_ERR_UNKNOWN;
+    }
+
+    return 0;
+}
+
+static struct argp argp = { options, parse_opt, args_doc, doc };
+struct arguments   arguments;
+
+static int check_test(struct arguments* args, char* x)
+{
+    int i;
+
+    if (args->ntests == 0) {
+        return 1;
+    }
+    for (i = 0; i < args->ntests; i++) {
+        if (strcmp(x, args->tests[i]) == 0) {
+            return 1;
+        }
+    }
+    return 0;
+}
+
+#define TEST(x)                                                                \
+    do {                                                                       \
+        if (check_test(&arguments, #x)) {                                      \
+            x();                                                               \
+        }                                                                      \
+    } while (0)
+
+int main(int argc, char* argv[])
+{
+    argp_parse(&argp, argc, argv, 0, 0, &arguments);
+
+    UNITY_BEGIN();
+    TEST(test_persist_types);
+
+    return UNITY_END();
+}