test(gbrain-doctor): pin schema_version:2 doctor parse path (#1418)

Adds an exec-path regression test that runs a fake gbrain shim emitting
the v0.25+ doctor JSON shape (schema_version: 2, status: "warnings",
exit 1 for health_score < 100, no top-level `engine` field). Confirms
freshDetectEngineTier recovers stdout from the non-zero exit and falls
back to GBRAIN_HOME/config.json for the engine label.

The pre-existing test for #1415 only stripped gbrain from PATH; this
test exercises the actual doctor parse path, closing the gap that
codex's plan review flagged.

Also documents the schema_version separation in
lib/gbrain-local-status.ts: the local CacheEntry stays at version 1,
distinct from the doctor-output schema_version which we accept across
versions in gstack-memory-helpers.

Closes #1418 (credit @mvanhorn for surfacing the doctor + schema_v2
collapse). The fix landed pre-emptively in v1.29.x; this commit pins
it with a stronger test.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

lib/gbrain-local-status.ts

@@ -51,6 +51,12 @@ export interface ClassifyOptions {
 }
 
 interface CacheEntry {
+  // Local-cache schema version, controlled by gstack. Not to be confused
+  // with `gbrain doctor --json` output schema_version (gbrain v0.25+ emits
+  // schema_version: 2). Doctor-output parsing lives in
+  // lib/gstack-memory-helpers.ts:freshDetectEngineTier and accepts both
+  // doctor-output versions. This cache stays strictly at version 1 — a
+  // future shape change here requires an explicit migration.
   schema_version: 1;
   status: LocalEngineStatus;
   cached_at: number;

test/gstack-memory-helpers.test.ts

@@ -341,4 +341,41 @@ describe("detectEngineTier", () => {
     const result = detectEngineTier();
     expect(result.engine).toBe("supabase");
   });
+
+  it("parses schema_version:2 doctor JSON via the exec path (regression for #1418)", () => {
+    // Stronger pin than the PATH-stripped fallback above: install a fake
+    // gbrain shim that successfully exits with status 1 (health_score < 100,
+    // mirroring real-world Supabase brains) and emits the v2 doctor JSON
+    // shape — schema_version: 2, status: "warnings", no top-level `engine`.
+    // The parser must still produce a usable EngineDetect by falling back
+    // to GBRAIN_HOME/config.json when `engine` is absent from doctor output.
+    const binDir = mkdtempSync(join(tmpdir(), "gstack-gbrain-shim-"));
+    const shim = join(binDir, "gbrain");
+    writeFileSync(
+      shim,
+      `#!/bin/sh
+if [ "$1" = "doctor" ]; then
+  cat <<'JSON'
+{"schema_version":2,"status":"warnings","health_score":90,"checks":[{"name":"resolver_health","status":"ok","message":"42 skills"}]}
+JSON
+  exit 1
+fi
+if [ "$1" = "--version" ]; then
+  echo "gbrain 0.35.0.0"
+  exit 0
+fi
+exit 0
+`,
+      { mode: 0o755 }
+    );
+    process.env.PATH = `${binDir}:${process.env.PATH || ""}`;
+    writeFileSync(
+      join(testGbrainHome, "config.json"),
+      JSON.stringify({ engine: "pglite" }),
+      "utf-8"
+    );
+    const result = detectEngineTier();
+    expect(result.engine).toBe("pglite");
+    rmSync(binDir, { recursive: true, force: true });
+  });
 });