feat(attachments): fondation pipeline durable d'attachments agent/chat + sandbox-safe (#154, QA verte)

Socle #154 : entité attachment, store, contrat DTO et routage session. Modules : domain/chat_attachment, application/chat_attachments, infrastructure/chat_attachments, app-tauri (commands/lib), backend dto.

crates/domain/src/ports.rs

@@ -34,6 +34,7 @@ use crate::agent_tool_policy::AgentToolPolicy;
 use crate::background_task::{
     BackgroundTask, BackgroundTaskKind, BackgroundTaskResult, BackgroundTaskWakePolicy,
 };
+use crate::chat_attachment::{ChatAttachment, ChatAttachmentId, ChatAttachmentSourceKind};
 use crate::device::{AuthenticatedDevice, DeviceId, PairedDevice};
 use crate::events::DomainEvent;
 use crate::ids::{
@@ -1066,6 +1067,57 @@ pub struct IssueAttachmentContent {
     pub bytes: Vec<u8>,
 }
 
+/// Metadata supplied by a driving adapter when importing a chat attachment.
+#[derive(Debug, Clone, PartialEq, Eq)]
+pub struct ChatAttachmentImport {
+    /// Stable id allocated by the application layer.
+    pub id: ChatAttachmentId,
+    /// Original display filename.
+    pub filename: String,
+    /// MIME type.
+    pub mime: String,
+    /// Origin kind.
+    pub source_kind: ChatAttachmentSourceKind,
+    /// Creation time, epoch milliseconds.
+    pub created_at: u64,
+}
+
+/// Chat attachment store errors.
+#[derive(Debug, Clone, PartialEq, Eq, Error)]
+pub enum ChatAttachmentStoreError {
+    /// The requested attachment does not exist.
+    #[error("chat attachment not found")]
+    NotFound,
+    /// The attachment payload is invalid.
+    #[error("chat attachment invalid: {0}")]
+    Invalid(String),
+    /// Store I/O or serialization failed.
+    #[error("chat attachment store failed: {0}")]
+    Store(String),
+}
+
+/// Persistence port for project-scoped agent/chat attachments.
+#[async_trait]
+pub trait ChatAttachmentStore: Send + Sync {
+    /// Copies a local source file into IdeA-managed durable attachment storage.
+    async fn import_from_path(
+        &self,
+        root: &ProjectPath,
+        project_id: ProjectId,
+        agent_id: AgentId,
+        session_id: SessionId,
+        source: &LocalPath,
+        import: ChatAttachmentImport,
+    ) -> Result<ChatAttachment, ChatAttachmentStoreError>;
+
+    /// Lists attachments imported for a structured/chat session.
+    async fn list_for_session(
+        &self,
+        root: &ProjectPath,
+        session_id: SessionId,
+    ) -> Result<Vec<ChatAttachment>, ChatAttachmentStoreError>;
+}
+
 /// Errors from the sprint store.
 #[derive(Debug, Clone, PartialEq, Eq, Error)]
 pub enum SprintStoreError {