feat(fof-layer2): Tauri commands + frontend compose/comment routing

Three new Tauri commands surface Layer 2 to the frontend:

- create_post_with_fof_comments(content) → { postId }
  Builds the FoF gating block from the default persona's keyring and
  publishes a Mode 2 post (public body, FoF-gated comments).
- comment_on_fof_post(post_id_hex, body)
  Backwards-compat wrapper: comment_on_post now auto-detects FoF
  gating on the parent post and dispatches internally. Existing
  comment-send UI works unchanged.
- revoke_fof_commenter(post_id_hex, pub_x_index, reason_code)
  Wraps the Node helper. UI for per-comment revocation can hang off
  this without further Node changes.

Node::comment_on_post now branches on parent post fof_gating presence
— this is the central routing point so neither the frontend nor
existing comment-send code needs to know about FoF specifics. FoF
posts get FoF comments automatically; non-FoF posts get the legacy
path. Same Tauri command, same frontend handler.

Frontend:
- Compose: comment-perm-select gains a "Friends of Friends" option.
  When picked, compose dispatches to create_post_with_fof_comments
  instead of the standard create_post. Standard set_comment_policy
  diff fires after so receivers' four-check accept rule activates.
- Attachments + non-default-persona FoF posts are out-of-v1; compose
  reports + aborts rather than silently producing a non-FoF post.

Layer 2 backend + minimal-viable UI complete. Granular per-comment
revoke UI and access-grant UI deferred — Node + Tauri primitives
exist; the surfaces can be added without further crypto work.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

crates/tauri-app/src/lib.rs

@@ -1145,6 +1145,53 @@ async fn list_vouches_received(state: State<'_, AppNode>) -> Result<Vec<VouchRec
     }).collect())
 }
 
+// --- FoF Layer 2: comment-gated post + commenting ---
+
+#[derive(Serialize)]
+#[serde(rename_all = "camelCase")]
+struct FoFPostCreatedDto {
+    post_id: String,
+}
+
+#[tauri::command]
+async fn create_post_with_fof_comments(
+    state: State<'_, AppNode>,
+    content: String,
+) -> Result<FoFPostCreatedDto, String> {
+    let node = get_node(&state).await;
+    let (post_id, _post, _vis, _cek) = node
+        .create_post_with_fof_comments(content, vec![])
+        .await
+        .map_err(|e| e.to_string())?;
+    Ok(FoFPostCreatedDto { post_id: hex::encode(post_id) })
+}
+
+#[tauri::command]
+async fn comment_on_fof_post(
+    state: State<'_, AppNode>,
+    post_id_hex: String,
+    body: String,
+) -> Result<(), String> {
+    let node = get_node(&state).await;
+    let pid = parse_node_id(&post_id_hex)?; // PostId is also [u8; 32]
+    node.comment_on_fof_post(pid, body).await
+        .map(|_| ())
+        .map_err(|e| e.to_string())
+}
+
+#[tauri::command]
+async fn revoke_fof_commenter(
+    state: State<'_, AppNode>,
+    post_id_hex: String,
+    pub_x_index: u32,
+    reason_code: u8,
+) -> Result<(), String> {
+    let node = get_node(&state).await;
+    let pid = parse_node_id(&post_id_hex)?;
+    node.revoke_fof_commenter(pid, pub_x_index, reason_code).await
+        .map_err(|e| e.to_string())
+}
+
 #[tauri::command]
 async fn list_follows(state: State<'_, AppNode>) -> Result<Vec<PeerDto>, String> {
     let node = get_node(&state).await;
@@ -3163,6 +3210,9 @@ pub fn run() {
             revoke_vouch_for_peer,
             list_vouches_given,
             list_vouches_received,
+            create_post_with_fof_comments,
+            comment_on_fof_post,
+            revoke_fof_commenter,
             list_circles,
             create_circle,
             delete_circle,