fix: align planner plan contract with phase index (#3436)

* test: add planner/query contract regressions (#3430)

* fix: align planner plan contract with phase index (#3430)

* docs: add changeset for #3430

* fix: keep planner contract docs within size budget (#3430)

* docs: set changeset pr for #3430

tests/bug-3430-planner-phase-contract.test.cjs

@@ -0,0 +1,44 @@
+// allow-test-rule: source-text-is-the-product
+// Planner markdown is the deployed planning contract; these checks lock the
+// exact canonical forms that downstream phase-plan-index accepts.
+
+'use strict';
+
+const { test } = require('node:test');
+const assert = require('node:assert/strict');
+const fs = require('node:fs');
+const path = require('node:path');
+
+const PLANNER_PATH = path.join(__dirname, '..', 'agents', 'gsd-planner.md');
+
+function readPlanner() {
+  return fs.readFileSync(PLANNER_PATH, 'utf8');
+}
+
+test('#3430: planner SUMMARY instruction uses canonical padded phase/plan form', () => {
+  const content = readPlanner();
+  assert.match(
+    content,
+    /Create `\.planning\/phases\/XX-name\/\{padded_phase\}-\{plan\}-SUMMARY\.md` when done/,
+    'planner must instruct executors to write SUMMARY files in canonical padded-phase form'
+  );
+  assert.doesNotMatch(
+    content,
+    /After completion, create `\.planning\/phases\/XX-name\/\{phase\}-\{plan\}-SUMMARY\.md`/,
+    'planner must not instruct the broken {phase}-{plan}-SUMMARY.md form'
+  );
+});
+
+test('#3430: planner depends_on docs show canonical in-phase plan ids', () => {
+  const content = readPlanner();
+  assert.match(
+    content,
+    /depends_on:[^\n]*Use `01-01`\/`01-01-auth-hardening`/,
+    'planner must document canonical depends_on examples that phase-plan-index resolves'
+  );
+  assert.doesNotMatch(
+    content,
+    /depends_on:[^\n]*01-trust\/01/,
+    'planner must not document phase-slug/plan-number depends_on examples as canonical'
+  );
+});