P2: file operations with dialogs (mkdir, new file, rename, delete, chmod)

- prompt/confirm/chmod dialogs (signals-driven via DialogsService)
- FileActionsService: acts on selection or cursor row of the active panel
- function bar + F2/F7/F8/Delete keys; delete confirms and recurses
- verified provider ops + walkTree + removeRecursive on a scratch tree

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

ui/src/app/dialogs.service.ts

@@ -0,0 +1,40 @@
+import { Injectable, signal } from '@angular/core';
+
+export interface PromptRequest {
+  title: string;
+  placeholder?: string;
+  initial?: string;
+  confirmLabel: string;
+  onConfirm: (value: string) => void;
+}
+
+export interface ConfirmRequest {
+  title: string;
+  body: string;
+  confirmLabel: string;
+  destructive?: boolean;
+  onConfirm: () => void;
+}
+
+export interface ChmodRequest {
+  targets: string[]; // display names
+  initialMode: number;
+  onConfirm: (mode: number) => void;
+}
+
+@Injectable({ providedIn: 'root' })
+export class DialogsService {
+  readonly prompt = signal<PromptRequest | null>(null);
+  readonly confirm = signal<ConfirmRequest | null>(null);
+  readonly chmod = signal<ChmodRequest | null>(null);
+
+  get anyOpen(): boolean {
+    return !!(this.prompt() || this.confirm() || this.chmod());
+  }
+
+  closeAll(): void {
+    this.prompt.set(null);
+    this.confirm.set(null);
+    this.chmod.set(null);
+  }
+}