test: align cross-cutting pins with the wave's contracts

Three suites pinned pre-wave behavior: browse's gstack-config test asserted
the old unknown-key ''/exit-0 shape (#2611 made it exit 1); the Windows-paths
suite pinned O_APPEND enqueue atomicity (the spool design satisfies the same
invariant via tmp + os.replace, one file per record — pinned in its new
form); and nine carve-guard skeleton ceilings absorbed the #2402
unconditional-learnings prose (~450B per skill), bumped with measured values
per the guard's own protocol.

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

browse/test/gstack-config.test.ts

@@ -56,9 +56,11 @@ describe('gstack-config', () => {
     expect(stdout).toBe('false');
   });
 
-  test('get unknown key on missing file returns empty, exit 0', () => {
+  test('get unknown key on missing file returns empty, exit 1 (#2611)', () => {
+    // #2611: an unknown key exits 1 so `|| echo fallback` callers can fire —
+    // "" with exit 0 was indistinguishable from a real empty value.
     const { exitCode, stdout } = run(['get', 'some_unknown_key']);
-    expect(exitCode).toBe(0);
+    expect(exitCode).toBe(1);
     expect(stdout).toBe('');
   });
 
@@ -69,10 +71,10 @@ describe('gstack-config', () => {
     expect(stdout).toBe('true');
   });
 
-  test('get missing key returns empty', () => {
+  test('get missing key returns empty, exit 1 (#2611)', () => {
     writeFileSync(join(stateDir, 'config.yaml'), 'auto_upgrade: true\n');
     const { exitCode, stdout } = run(['get', 'nonexistent']);
-    expect(exitCode).toBe(0);
+    expect(exitCode).toBe(1);
     expect(stdout).toBe('');
   });