fix: reject empty scaffold plan files in plan-slice artifact verification (#699)

verifyExpectedArtifact() for plan-slice units only checked whether the
plan file existed on disk, not whether it contained actual task entries.
When a plan file was created as an empty scaffold during discussion/context
(headings but no tasks), the artifact check considered it 'complete' and
skipped the dispatch. Since deriveState still returned phase:'planning'
(no tasks found), this created an infinite skip loop until auto-mode
exhausted its retry budget and stopped silently.

Added a content check that requires at least one task entry matching
the pattern '- [ ] **T##:' or '- [x] **T##:' before considering a
plan-slice artifact valid. This mirrors the existing content-aware
check used for execute-task (which verifies checkbox state).

Added 3 regression tests covering empty scaffold, valid tasks, and
completed tasks.

src/resources/extensions/gsd/auto-recovery.ts

@@ -130,6 +130,16 @@ export function verifyExpectedArtifact(unitType: string, unitId: string, base: s
   if (!absPath) return unitType === "replan-slice";
   if (!existsSync(absPath)) return false;
 
+  // plan-slice must produce a plan with actual task entries, not just a scaffold.
+  // The plan file may exist from a prior discussion/context step with only headings
+  // but no tasks. Without this check the artifact is considered "complete" and the
+  // unit gets skipped — but deriveState still returns phase:"planning" because the
+  // plan has no tasks, creating an infinite skip loop (#699).
+  if (unitType === "plan-slice") {
+    const planContent = readFileSync(absPath, "utf-8");
+    if (!/^- \[[xX ]\] \*\*T\d+:/m.test(planContent)) return false;
+  }
+
   // execute-task must also have its checkbox marked [x] in the slice plan
   if (unitType === "execute-task") {
     const parts = unitId.split("/");

src/resources/extensions/gsd/tests/auto-recovery.test.ts

@@ -320,3 +320,67 @@ test("verifyExpectedArtifact detects roadmap [x] change despite parse cache", ()
     cleanup(base);
   }
 });
+
+// ─── verifyExpectedArtifact: plan-slice empty scaffold regression (#699) ──
+
+test("verifyExpectedArtifact rejects plan-slice with empty scaffold", () => {
+  const base = makeTmpBase();
+  try {
+    const sliceDir = join(base, ".gsd", "milestones", "M001", "slices", "S01");
+    mkdirSync(sliceDir, { recursive: true });
+    writeFileSync(join(sliceDir, "S01-PLAN.md"), "# S01: Test Slice\n\n## Tasks\n\n");
+    assert.strictEqual(
+      verifyExpectedArtifact("plan-slice", "M001/S01", base),
+      false,
+      "Empty scaffold should not be treated as completed artifact",
+    );
+  } finally {
+    cleanup(base);
+  }
+});
+
+test("verifyExpectedArtifact accepts plan-slice with actual tasks", () => {
+  const base = makeTmpBase();
+  try {
+    const sliceDir = join(base, ".gsd", "milestones", "M001", "slices", "S01");
+    mkdirSync(sliceDir, { recursive: true });
+    writeFileSync(join(sliceDir, "S01-PLAN.md"), [
+      "# S01: Test Slice",
+      "",
+      "## Tasks",
+      "",
+      "- [ ] **T01: Implement feature** `est:2h`",
+      "- [ ] **T02: Write tests** `est:1h`",
+    ].join("\n"));
+    assert.strictEqual(
+      verifyExpectedArtifact("plan-slice", "M001/S01", base),
+      true,
+      "Plan with task entries should be treated as completed artifact",
+    );
+  } finally {
+    cleanup(base);
+  }
+});
+
+test("verifyExpectedArtifact accepts plan-slice with completed tasks", () => {
+  const base = makeTmpBase();
+  try {
+    const sliceDir = join(base, ".gsd", "milestones", "M001", "slices", "S01");
+    mkdirSync(sliceDir, { recursive: true });
+    writeFileSync(join(sliceDir, "S01-PLAN.md"), [
+      "# S01: Test Slice",
+      "",
+      "## Tasks",
+      "",
+      "- [x] **T01: Implement feature** `est:2h`",
+      "- [ ] **T02: Write tests** `est:1h`",
+    ].join("\n"));
+    assert.strictEqual(
+      verifyExpectedArtifact("plan-slice", "M001/S01", base),
+      true,
+      "Plan with completed task entries should be treated as completed artifact",
+    );
+  } finally {
+    cleanup(base);
+  }
+});