fix: bind Web Push mutations to exact authority

WP-01: a CAS receipt is only evidence when it names the expected key and the
exact next revision. Write and remove now share one validator, so a stale or
arbitrary repository receipt can no longer be packaged as a confirmed control.

WP-05: a pre-aborted command records the operation the caller requested instead
of always reporting an inspection.

WP-06: bounded fan-out is reported honestly. The subscriptionchange client
handoff and the notification cleanup both emit countBucket and truncated, and an
incomplete cleanup returns { complete: false } and is observed as DEGRADED
separately from revoke authority.

WP-07: the user-visible native notification effect is tracked through
NOT_APPLIED, MAYBE_APPLIED and CONFIRMED phases and surfaced as observation
evidence, never as retry authorization.

WP-02, WP-03 and WP-04 stay open: they need the V2 wire protocol with server
request-shape negotiation, which belongs to the versioned-migration task rather
than this correctness pass. The ledger records them as DEFERRED_TO_MIGRATION.

Web Push remains NOT_SELECTED and AVAILABLE_NOT_COMPOSED.

Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>

tests/unit/web-push-fence-store.test.ts

@@ -42,6 +42,37 @@ function manualScheduler() {
 }
 
 describe("Web Push durable control fence", () => {
+  it.each([0, 2, 3, 9_999])(
+    "rejects a CAS receipt that is not the exact next revision (%i)",
+    async (revision) => {
+      // WP-01. Only the exact next revision is evidence that this command
+      // actually wrote the control it claims to have written.
+      const dependencies = createFakePushControlStoreDependencies();
+      const repository = dependencies.repository;
+      const compareAndSwap = repository.compareAndSwap.bind(repository);
+      repository.compareAndSwap = async (input) => {
+        const written = await compareAndSwap(input);
+        return written.ok
+          ? {
+              ok: true as const,
+              value: { ...written.value, revision },
+            }
+          : written;
+      };
+      const store = createPushAssociationFenceStore(dependencies);
+
+      await expect(
+        store.prepare({
+          authority: firstAuthority,
+          updatedAt: "2026-07-28T00:00:00.000Z",
+        }),
+      ).resolves.toMatchObject({
+        ok: false,
+        error: { code: "CONTROL_CORRUPT" },
+      });
+    },
+  );
+
   it("CASes UNASSOCIATED to ACTIVE and prevents tombstone resurrection", async () => {
     const store = createPushAssociationFenceStore(
       createFakePushControlStoreDependencies(),