test: add failing regression for #2073 agy reviewer invocation shape

The agy block in /gsd-review overflows the exec arg list (inline "$(cat)"),
has no external timeout (pre-session stall hangs past --print-timeout), no
--model escape hatch for a 404'd pinned model, a generic empty-output stub,
and a stale 'no --model flag' note. These tests pin the corrected shape in
gsd-core/workflows/review.md; they fail on next.

tests/antigravity-reviewer.test.cjs

@@ -0,0 +1,105 @@
+// allow-test-rule: source-text-is-the-product
+// gsd-core/workflows/review.md is a workflow document whose bash blocks ARE
+// what /gsd-review loads and executes at runtime. Asserting the Antigravity
+// invocation shape asserts the deployed contract — this is behavioral coverage
+// of the workflow, not a source-grep over application code.
+
+/**
+ * Antigravity (agy) reviewer invocation tests (#2073)
+ *
+ * The agy block in /gsd-review had three real-world failure modes on agy 1.0.16:
+ *   1. inline `-p "$(cat <prompt>)"` overflowed the exec arg list on a large prompt
+ *   2. a pinned model that 404'd exited 0 with empty stdout AND an empty transcript
+ *      (no --model escape hatch; the generic Step 3 stub gave no diagnostic)
+ *   3. a pre-session stall hung past --print-timeout (which can't fire before a
+ *      session exists) because there was no external wall-clock `timeout`
+ * Plus a stale maintainer note claiming agy has no --model flag.
+ *
+ * These tests pin the corrected invocation shape in gsd-core/workflows/review.md.
+ */
+
+const { test, describe } = require('node:test');
+const assert = require('node:assert/strict');
+const fs = require('fs');
+const path = require('path');
+
+const ROOT = path.join(__dirname, '..');
+const REVIEW_PATH = path.join(ROOT, 'gsd-core', 'workflows', 'review.md');
+
+function agyBashBlock() {
+  const content = fs.readFileSync(REVIEW_PATH, 'utf-8');
+  const fences = content.match(/```bash[\s\S]*?```/g) || [];
+  // Target the INVOCATION block (the fence that writes the antigravity review
+  // output), not the `command -v agy` detection one-liner.
+  const agy = fences.find((f) => /\bagy\b/.test(f) && /gsd-review-antigravity/.test(f));
+  assert.ok(agy, 'review.md should contain the agy invocation bash block');
+  return agy;
+}
+
+describe('Antigravity (agy) reviewer invocation in /gsd-review (#2073)', () => {
+  test('review.md exists', () => {
+    assert.ok(fs.existsSync(REVIEW_PATH), 'review.md should exist');
+  });
+
+  test('#2073 mode 1 — does NOT inline the prompt via "$(cat ...)" (arg-list overflow)', () => {
+    const block = agyBashBlock();
+    assert.ok(
+      !/"\$\(cat/.test(block),
+      'agy must not inline the prompt via "$(cat …)" — a large review prompt overflows the exec arg list',
+    );
+  });
+
+  test('#2073 mode 1 — uses a file-reference prompt (mirrors the Cursor block)', () => {
+    const block = agyBashBlock();
+    assert.ok(
+      /Read the file at \/tmp\/gsd-review-prompt-/.test(block),
+      'agy should reference the prompt by file path, not inline it',
+    );
+  });
+
+  test('#2073 mode 3 — invocation is wrapped in an external wall-clock timeout', () => {
+    const block = agyBashBlock();
+    assert.ok(
+      /(^|\s)timeout\s+\d/.test(block),
+      'agy invocation must be wrapped in an external `timeout <secs>` — --print-timeout cannot fire before agy creates a session',
+    );
+  });
+
+  test('#2073 mode 3 — stdin is tied to /dev/null (no tty stall)', () => {
+    const block = agyBashBlock();
+    assert.ok(
+      /<\/dev\/null/.test(block),
+      'agy invocation should redirect stdin from /dev/null so it never blocks on a tty',
+    );
+  });
+
+  test('#2073 mode 2 — wires review.models.agy via --model when configured', () => {
+    const block = agyBashBlock();
+    assert.ok(/--model/.test(block), 'agy block should pass --model when AGY_MODEL is set');
+    assert.ok(/AGY_MODEL/.test(block), 'agy block should reference the AGY_MODEL config variable');
+  });
+
+  test('#2073 mode 2 — Step 3 stub surfaces a diagnostic from agy cli.log (not just a generic stub)', () => {
+    const block = agyBashBlock();
+    assert.ok(
+      /cli\.log/.test(block),
+      'the empty-output stub should inspect agy cli.log for a model-availability diagnostic (NOT_FOUND / agent executor error)',
+    );
+  });
+
+  test('#2073 — stale "no --model flag" maintainer note is corrected', () => {
+    const content = fs.readFileSync(REVIEW_PATH, 'utf-8');
+    assert.ok(
+      !/No .{0,4}-m.{0,4}\/.{0,4}--model.{0,4} flag/i.test(content),
+      'the stale maintainer note claiming agy has no --model flag must be corrected (--model exists since ~1.0.3)',
+    );
+  });
+
+  test('#2073 — review.models.agy is documented as supported (not "reserved for future")', () => {
+    const content = fs.readFileSync(REVIEW_PATH, 'utf-8');
+    assert.ok(
+      !/review\.models\.agy is reserved for future/i.test(content),
+      'review.models.agy is now wired (passed as --model); the "reserved for future" comment must be updated',
+    );
+  });
+});