feat(agent): reprise des sessions au redémarrage (B2) — commande + ResumeProjectPanel

- Tauri : commande list_resumable_agents (projectId) + ResumableAgentListDto
  { resumable } / ResumableAgentDto (camelCase, conversationId omis si None),
  câblage state.rs (réutilise stores + ProfileStore, aucun nouveau port).
- Front : gateway listResumableAgents, ResumeProjectPanel monté à l'ouverture
  de projet (opt-in, FR) : Reprendre (launch_agent nodeId+conversationId),
  Nouvelle conversation (setCellConversation(null) puis launch), Ignorer,
  Tout reprendre/ignorer. resumeSupported=false ⇒ « relance à neuf ».
- doc : §15.2 coquille agents→resumable (alignée use case/back/front).

Tests : app-tauri dto 9/9 ; vitest 324 (+10) ; workspace Rust 0 échec. 0 régression.

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

crates/app-tauri/src/dto.rs

@@ -1305,6 +1305,72 @@ pub fn parse_agent_id(raw: &str) -> Result<AgentId, ErrorDto> {
         })
 }
 
+// ---------------------------------------------------------------------------
+// Resumable agents (§15.2 — Chantier B2)
+// ---------------------------------------------------------------------------
+
+use application::{ListResumableAgentsOutput, ResumableAgent};
+
+/// One resumable agent cell, as seen by the frontend (§15.2).
+///
+/// Mirrors [`ResumableAgent`]: the agent's identity + its host cell, the CLI
+/// conversation id to resume (absent ⇒ fresh relaunch), the `was_running` flag
+/// frozen at close, and whether the agent's profile can resume a CLI
+/// conversation. `conversationId` is **omitted from the wire when `None`**
+/// (`skip_serializing_if`), so the TypeScript side sees an absent key — not
+/// `null`.
+#[derive(Debug, Clone, Serialize)]
+#[serde(rename_all = "camelCase")]
+pub struct ResumableAgentDto {
+    /// The resumable agent's id (UUID string).
+    pub agent_id: String,
+    /// The agent's display name (resolved from the manifest).
+    pub name: String,
+    /// The host layout leaf where the agent is relaunched/resumed (UUID string).
+    pub node_id: String,
+    /// Persistent CLI conversation id carried by the cell. Absent ⇒ fresh
+    /// relaunch (no history to resume).
+    #[serde(skip_serializing_if = "Option::is_none")]
+    pub conversation_id: Option<String>,
+    /// The `agent_was_running` flag frozen at the cell's close.
+    pub was_running: bool,
+    /// `true` when the agent's profile carries a usable resume strategy.
+    pub resume_supported: bool,
+}
+
+impl From<ResumableAgent> for ResumableAgentDto {
+    fn from(r: ResumableAgent) -> Self {
+        Self {
+            agent_id: r.agent_id.to_string(),
+            name: r.name,
+            node_id: r.node_id.to_string(),
+            conversation_id: r.conversation_id,
+            was_running: r.was_running,
+            resume_supported: r.resume_supported,
+        }
+    }
+}
+
+/// Response DTO for `list_resumable_agents` (§15.2).
+#[derive(Debug, Clone, Serialize)]
+#[serde(rename_all = "camelCase")]
+pub struct ResumableAgentListDto {
+    /// The resumable agent cells, in layout-traversal order.
+    pub resumable: Vec<ResumableAgentDto>,
+}
+
+impl From<ListResumableAgentsOutput> for ResumableAgentListDto {
+    fn from(out: ListResumableAgentsOutput) -> Self {
+        Self {
+            resumable: out
+                .resumable
+                .into_iter()
+                .map(ResumableAgentDto::from)
+                .collect(),
+        }
+    }
+}
+
 // ---------------------------------------------------------------------------
 // Templates & sync (L7)
 // ---------------------------------------------------------------------------