feat(contract): lanes run gstack-pregate (and the sealed guard where configured) before done; handoff carries the gstack trailer and PREGATE: line

The coordinator contract gains a 'Before done' paragraph and the handoff
order GSTACK_RESULT, gstack: ok|fail <rev>, PREGATE:, gate summary; the
spec section is regenerated and docs/unattended.md states the same rule.
A new test pins the terms and their order; the byte-identity pins stay.

Co-authored-by: capy-ai[bot] <230910855+capy-ai[bot]@users.noreply.github.com>

test/lane-coordination.test.ts

@@ -129,6 +129,15 @@ describe('coordinator contract', () => {
     expect(rendered).toContain('gstack-autoplan contract) || {');
   });
 
+  test('field wave CD: a lane runs pregate (and the sealed guard where configured) before done; the handoff carries the gstack trailer and the PREGATE: line after GSTACK_RESULT', () => {
+    expect(COORDINATOR_CONTRACT).toContain('`gstack-pregate run --allow-repo-commands`');
+    expect(COORDINATOR_CONTRACT).toContain('`gstack-pregate sealed` before any push or PR creation');
+    const handoff = COORDINATOR_CONTRACT.slice(COORDINATOR_CONTRACT.indexOf('Handoff format.'));
+    const order = ['`GSTACK_RESULT` line', '`gstack: ok|fail <rev>` line', '`PREGATE:` line', 'gate summary'].map(t => handoff.indexOf(t));
+    expect(order.every(i => i > 0)).toBe(true);
+    expect([...order].sort((a, b) => a - b)).toEqual(order);
+  });
+
   test('both reviewer prompts carry the contract after the plan, labelled as data', async () => {
     const { writePrompts } = await import('../lib/autoplan-prompts');
     const dir = fs.mkdtempSync(path.join(require('node:os').tmpdir(), 'gstack-contract-'));