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/p4.ts

@@ -71,6 +71,7 @@ export const p4 = {
   streams: () => invoke<{ Stream?: string; Name?: string; Type?: string; Parent?: string; [k: string]: unknown }[]>("p4_streams"),
   switchStream: (stream: string) => invoke<P4Info>("p4_switch_stream", { stream }),
   streamInteg: (stream: string, direction: "down" | "up") => invoke<string>("p4_stream_integ", { stream, direction }),
+  filelog: (depot: string) => invoke<Record<string, unknown>>("p4_filelog", { depot }),
   jobs: () => invoke<{ Job?: string; Status?: string; Description?: string; User?: string; [k: string]: unknown }[]>("p4_jobs"),
   fix: (job: string, change: string) => invoke<string>("p4_fix", { job, change }),
   jobSpec: (job: string) => invoke<string>("p4_job_spec", { job }),
@@ -179,6 +180,26 @@ export function leaf(path?: string): string {
   return p.slice(p.lastIndexOf("/") + 1);
 }
 
+// per-file revision history parsed from p4 filelog's indexed fields
+export interface FileRev { rev: string; change: string; action: string; user: string; time: string; desc: string; type: string }
+export function filelogRevs(v: Record<string, unknown>): FileRev[] {
+  const out: FileRev[] = [];
+  for (let i = 0; ; i++) {
+    const rev = v[`rev${i}`] as string | undefined;
+    if (rev == null) break;
+    out.push({
+      rev,
+      change: (v[`change${i}`] as string) || "",
+      action: (v[`action${i}`] as string) || "",
+      user: (v[`user${i}`] as string) || "",
+      time: (v[`time${i}`] as string) || "",
+      desc: (v[`desc${i}`] as string) || "",
+      type: (v[`type${i}`] as string) || "",
+    });
+  }
+  return out;
+}
+
 // a submitted changelist with indexed file fields (depotFile0, action0, ...)
 export interface Describe extends Change { [k: string]: unknown }
 export function describeFiles(d: Describe): { depotFile: string; action: string; rev: string }[] {