test(cli): clean up before failing the install-plan receipt fixture

cli_install_plan_receipt_no_mutation_issue388 asserted inline, so any failure
returned before free(json) and test_rmdir_r(tmpdir). A red run therefore leaked
the receipt and left a stray /tmp/cli-plan-* directory behind -- the failure
report was accompanied by exactly the noise that makes the next debugging
session harder.

Record what went wrong, release everything, then fail. The message now names
the specific missing marker rather than reporting that some marker was absent,
which is the difference between reading a failure and bisecting one.

The env-isolation half of the original PR is not carried over: main's
tf_setup_cache_sentinel already unsets CODEX_HOME along with every other client
home override, so a per-test save/unset/restore would be redundant now.

Distilled from DeusData#1149 by Anand Aiyer, which predates that sentinel and could not
land as written once its companion PR closed unmerged.

Co-authored-by: Anand Aiyer <anand@aiyer.com>
Signed-off-by: Martin Vogel <martin.vogel.tech@gmail.com>

Author: DeusData

tests/test_cli.c

@@ -4447,24 +4447,55 @@ TEST(cli_install_plan_receipt_no_mutation_issue388) {
     test_mkdirp(dir);
 
     char *json = cbm_build_install_plan_json(tmpdir, "/usr/local/bin/codebase-memory-mcp");
-    ASSERT_NOT_NULL(json);
-    ASSERT(strstr(json, "agent.install.plan.v1") != NULL);
-    ASSERT(strstr(json, "writes_started") != NULL);
-    ASSERT(strstr(json, "next_safe_command") != NULL);
-    ASSERT(strstr(json, "cursor") != NULL);
-    ASSERT(strstr(json, ".cursor/mcp.json") != NULL);
-    ASSERT(strstr(json, ".codex/config.toml") != NULL);
+
+    /* WHY the failures are deferred: asserting inline returns before the free
+     * and the rmdir below, so every red run leaked the receipt and left a
+     * stray /tmp/cli-plan-* directory behind. That makes the next debugging
+     * session harder than the failure it is reporting. Record what went wrong,
+     * release everything, then fail -- and name the specific marker, because
+     * "a marker was missing" costs a reader a bisect that "next_safe_command
+     * was missing" does not. */
+    const char *missing = NULL;
+    if (!json) {
+        missing = "receipt was NULL";
+    } else {
+        static const char *const required[] = {
+            "agent.install.plan.v1", "writes_started",     "next_safe_command", "cursor",
+            ".cursor/mcp.json",      ".codex/config.toml",
+        };
+        for (size_t i = 0; i < sizeof(required) / sizeof(required[0]); i++) {
+            if (!strstr(json, required[i])) {
+                missing = required[i];
+                break;
+            }
+        }
+    }
     free(json);
 
     /* Critical: building the plan must NOT have created any config file. */
     char cfg[512];
     struct stat st;
+    const char *created = NULL;
     snprintf(cfg, sizeof(cfg), "%s/.cursor/mcp.json", tmpdir);
-    ASSERT(stat(cfg, &st) != 0); /* must not exist */
+    if (stat(cfg, &st) == 0) {
+        created = ".cursor/mcp.json";
+    }
     snprintf(cfg, sizeof(cfg), "%s/.codex/config.toml", tmpdir);
-    ASSERT(stat(cfg, &st) != 0); /* must not exist */
+    if (!created && stat(cfg, &st) == 0) {
+        created = ".codex/config.toml";
+    }
 
     test_rmdir_r(tmpdir);
+
+    char reason[256];
+    if (missing) {
+        snprintf(reason, sizeof(reason), "install plan receipt is missing %s", missing);
+        FAIL(reason);
+    }
+    if (created) {
+        snprintf(reason, sizeof(reason), "building an install plan created %s", created);
+        FAIL(reason);
+    }
     PASS();
 }