feat(session-limits): LS8-front — filet humain niveau 3 (saisie d'heure de reprise)

UI permettant à l'humain de renseigner l'heure de reprise quand le
niveau 2 détecte une limite sans heure exploitable.

- ports/index.ts : setResumeAt(agentId, resetsAtMs) sur InputGateway.
- adapters/input.ts : setResumeAt → invoke("set_resume_at").
- adapters/mock/index.ts : MockInputGateway.setResumeAt (resumeArmings[]).
- features/agents/useAgents.ts : action setResumeAt (sans mutation optimiste).
- features/agents/AgentLimitBadge.tsx : formulaire de saisie d'heure sur
  l'état suspected sans heure + helper pur timeInputToEpochMs (TODO LS7 retiré).
- features/agents/AgentsPanel.tsx : câblage onSetResumeAt.

Tests AgentLimitBadge.test.tsx mis à jour au nouveau contrat + couverture LS8 ;
typecheck propre, suite agents verte.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

frontend/src/ports/index.ts

@@ -561,6 +561,15 @@ export interface InputGateway {
    * `agentResumeCancelled` on success, which clears the countdown in the UI.
    */
   cancelResume(agentId: string): Promise<boolean>;
+  /**
+   * Human net (level 3, ARCHITECTURE §21.1): arms a resume at a user-chosen
+   * instant for an agent whose limit was *suspected* without a reliable reset
+   * time. `resetsAtMs` is the chosen wake-up in epoch-milliseconds; the backend
+   * clamps a past instant to "now" (⇒ immediate resume). This arms the same
+   * cancellable resume as the automatic path and re-emits `agentResumeScheduled`,
+   * so the UI flips on its own from "heure inconnue" to the nominal countdown.
+   */
+  setResumeAt(agentId: string, resetsAtMs: number): Promise<void>;
 }
 
 /**