⏭️ feat: Honor an Interrupt Before the Model Has Answered (#15491)

* ⏭️ feat: Honor an Interrupt Before the Model Has Answered

An interrupt armed while the model is still thinking sat as "Interrupting"
until the entire turn finished, then landed as a terminal continuation. The
cause is upstream: the SDK reads `shouldPreempt` once per streamed chunk, and
its seal gate requires non-empty text — so a silent provider is never polled at
all, and a reasoning-only turn is never sealable.

`@librechat/agents` gains a discard-and-restart path for exactly that window
(`HOOK_PREEMPT_RESTART_CAPABLE`). This wires the host half:

- `GenerationJobManager.subscribePreempt` registers run-scoped wake listeners,
  notified after an ACCEPTED arm — local or cross-replica, since both land in
  `armPreemptIds`. Fenced on `createdAt` like every other preempt entry point,
  and a throwing listener never fails the arm a queued steer depends on.
- `createSteerPreemptPoll` hands that channel to the SDK as
  `StreamPreemption.subscribe`, gated on a new `isSteerPreemptRestartSupported`
  probe so an SDK that cannot act on a wake is never handed one.

The wake is a hint only: `isPreemptRequested` stays the single authority, so
the level-triggered contract the seal path depends on is unchanged.

Inert until `@librechat/agents` publishes the restart contract — the probe
returns false against the pinned 3.7.11 and the run keeps today's behavior.

* 🩹 fix: Replay an Already-Armed Preempt on Subscribe

Preempt requests are level-triggered, and the window between a job becoming
steerable and the SDK installing its model-attempt listener is real. An
interrupt landing there was recorded with no callbacks to notify, and on a
silent or reasoning-only turn no later chunk poll may ever run — leaving the
request to wait out the whole turn, the exact stall this channel removes.

`subscribePreempt` now replays an existing arm to the newly registered listener
only, after registration: waking the whole set would re-notify runs that
already looked, and waking before registration would leave a concurrent arm
with nowhere to land. The `createdAt` fence is unchanged and still gates the
replay.

The SDK also reads the level flag once at each attempt's start, so this is
belt-and-braces rather than the sole cover — but it makes the host correct on
its own terms instead of resting on when the SDK happens to look.

* 🔧 chore: Update @librechat/agents dependency to version 3.7.14 in package-lock.json and related package.json files

* 🔧 chore: Update dependencies in package-lock.json and package.json

- Bump versions for @humanfs/core (0.19.1 to 0.19.2), @humanfs/node (0.16.6 to 0.16.8), @xmldom/xmldom (0.8.13 to 0.8.15), and qs (6.15.2 to 6.16.0).
- Add @humanfs/types (0.15.0) as a new dependency for @humanfs/node.
- Update dependencies for side-channel and side-channel-list to their latest versions.

api/server/controllers/agents/client.js

@@ -640,7 +640,7 @@ class AgentClient extends BaseClient {
       hook: createSteerDrainHook(drainOptions),
       ...(isSteerPreemptSupported() && {
         preemptHook: createSteerPreemptBoundaryHook(drainOptions),
-        preemption: createSteerPreemptPoll(streamId),
+        preemption: createSteerPreemptPoll(streamId, this.jobCreatedAt),
       }),
       ...(isSteerTerminalContinuationSupported() && {
         terminalHook: createSteerTerminalContinuationHook(drainOptions),