feat(journal): execute frozen body inputs with durable delivery and erasure fences

crates/runtime-api/Cargo.toml

@@ -9,6 +9,7 @@ license.workspace = true
 api-macros = { workspace = true, features = ["reqwest", "axum"] }
 manifest.workspace = true
 protocol.workspace = true
+session-store.workspace = true
 serde = { workspace = true, features = ["derive"] }
 workdir.workspace = true
 

crates/runtime-api/src/lib.rs

@@ -836,6 +836,34 @@ pub struct SessionMaterialPinResponse {
     pub pin_id: String,
 }
 
+/// One body-bearing immutable slice. The byte budget includes slice metadata,
+/// but not the enclosing availability enum or the caller's durable Job envelope.
+#[derive(Clone, Debug, Serialize, Deserialize)]
+#[serde(deny_unknown_fields)]
+pub struct SessionRecordingCaptureRequest {
+    pub workspace_id: String,
+    pub source: SessionPublicSource,
+    pub expected_session_id: String,
+    pub start: session_store::capture::RecordingPosition,
+    pub max_entries: usize,
+    pub max_serialized_bytes: usize,
+}
+
+#[derive(Clone, Debug, Serialize, Deserialize)]
+#[serde(tag = "availability", rename_all = "snake_case")]
+pub enum SessionRecordingCaptureAvailability {
+    NotMaterialized {
+        session_id: String,
+    },
+    Captured {
+        slice: session_store::capture::RecordingCaptureSlice,
+    },
+    Unavailable {
+        reason: SessionPublicUnavailableReason,
+        message: String,
+    },
+}
+
 #[derive(Clone, Debug, Serialize, Deserialize)]
 #[serde(deny_unknown_fields)]
 pub struct SessionMaterialCatalogRequest {
@@ -1246,6 +1274,16 @@ pub trait RuntimeApi {
         #[body] request: SessionMaterialPinRequest,
     ) -> Result<SessionMaterialPinResponse, RuntimeApiError>;
 
+    #[post(
+        "/v1/session-public/recording-capture",
+        status = 200,
+        error_status = 400
+    )]
+    async fn session_recording_capture(
+        &self,
+        #[body] request: SessionRecordingCaptureRequest,
+    ) -> Result<SessionRecordingCaptureAvailability, RuntimeApiError>;
+
     #[post(
         "/v1/session-public/material/catalog",
         status = 200,
@@ -1730,6 +1768,13 @@ mod tests {
             Err(test_error(501))
         }
 
+        async fn session_recording_capture(
+            &self,
+            _request: SessionRecordingCaptureRequest,
+        ) -> Result<SessionRecordingCaptureAvailability, RuntimeApiError> {
+            Err(test_error(501))
+        }
+
         async fn session_material_catalog(
             &self,
             _request: SessionMaterialCatalogRequest,