Discord: thread bindings idle + max-age lifecycle (#27845) (thanks @osolmaz)

* refactor discord thread bindings to idle and max-age lifecycle

* fix: migrate legacy thread binding expiry and reduce hot-path disk writes

* refactor: remove remaining thread-binding ttl legacy paths

* fix: harden thread-binding lifecycle persistence

* Discord: fix thread binding types in message/reply paths

* Infra: handle win32 unknown inode in file identity checks

* Infra: relax win32 guarded-open identity checks

* Config: migrate threadBindings ttlHours to idleHours

* Revert "Infra: relax win32 guarded-open identity checks"

This reverts commit de94126771.

* Revert "Infra: handle win32 unknown inode in file identity checks"

This reverts commit 96fc5ddfb3.

* Discord: re-read live binding state before sweep unbind

* fix: add changelog note for thread binding lifecycle update (#27845) (thanks @osolmaz)

---------

Co-authored-by: Onur Solmaz <onur@textcortex.com>

src/auto-reply/reply/commands-subagents-focus.test.ts

@@ -112,7 +112,8 @@ function createFakeThreadBindingManager(initialBindings: FakeBinding[] = []) {
   );
 
   const manager = {
-    getSessionTtlMs: vi.fn(() => 24 * 60 * 60 * 1000),
+    getIdleTimeoutMs: vi.fn(() => 24 * 60 * 60 * 1000),
+    getMaxAgeMs: vi.fn(() => 0),
     getByThreadId: vi.fn((threadId: string) => byThread.get(threadId)),
     listBySessionKey: vi.fn((targetSessionKey: string) =>
       [...byThread.values()].filter((binding) => binding.targetSessionKey === targetSessionKey),
@@ -286,7 +287,7 @@ describe("/focus, /unfocus, /agents", () => {
         targetSessionKey: "agent:codex-acp:session-1",
         metadata: expect.objectContaining({
           introText:
-            "⚙️ codex-acp session active (auto-unfocus in 24h). Messages here go directly to this session.",
+            "⚙️ codex-acp session active (idle auto-unfocus after 24h inactivity). Messages here go directly to this session.",
         }),
       }),
     );