File history timeline (filelog) with diff-to-previous

- File history button in the preview header opens a per-file revision timeline
  (rev, changelist, action, user, date, description) with Diff to previous
- Backend p4 filelog -l; filelogRevs parser

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

src-tauri/src/lib.rs

@@ -1867,6 +1867,19 @@ async fn p4_latest_change(state: State<'_, AppState>, scope: String) -> Result<V
     Ok(v.into_iter().next().unwrap_or(Value::Null))
 }
 
+/// Full revision history of a single file (`p4 filelog -l`), including
+/// per-revision changelist, action, user, time and description. Returns the
+/// tagged object with rev0/change0/action0/… arrays.
+#[tauri::command]
+async fn p4_filelog(state: State<'_, AppState>, depot: String) -> Result<Value, String> {
+    let conn = current(&state)?;
+    if depot.trim().is_empty() {
+        return Err("No file".into());
+    }
+    let v = run_json(&conn, &["filelog", "-l", "-m", "150", depot.trim()])?;
+    Ok(v.into_iter().next().unwrap_or(Value::Null))
+}
+
 /// List jobs on the server (defect/task tracking).
 #[tauri::command]
 async fn p4_jobs(state: State<'_, AppState>) -> Result<Vec<Value>, String> {
@@ -2209,6 +2222,7 @@ pub fn run() {
             p4_streams,
             p4_switch_stream,
             p4_stream_integ,
+            p4_filelog,
             p4_jobs,
             p4_fix,
             p4_job_spec,