feat: misc tool alignment (#137)

src/tools/impl/EnterPlanMode.ts

@@ -0,0 +1,32 @@
+interface EnterPlanModeArgs {
+  [key: string]: never;
+}
+
+interface EnterPlanModeResult {
+  message: string;
+}
+
+export async function enter_plan_mode(
+  _args: EnterPlanModeArgs,
+): Promise<EnterPlanModeResult> {
+  // This is handled by the UI layer which will:
+  // 1. Show approval dialog
+  // 2. On approve: toggle plan mode on, generate plan file path, inject system reminder
+  // 3. On reject: send rejection, agent proceeds without plan mode
+  //
+  // The message below is returned on successful entry into plan mode.
+  // The UI harness will also inject a <system-reminder> with the plan file path.
+  return {
+    message: `Entered plan mode. You should now focus on exploring the codebase and designing an implementation approach.
+
+In plan mode, you should:
+1. Thoroughly explore the codebase to understand existing patterns
+2. Identify similar features and architectural approaches
+3. Consider multiple approaches and their trade-offs
+4. Use AskUserQuestion if you need to clarify the approach
+5. Design a concrete implementation strategy
+6. When ready, use ExitPlanMode to present your plan for approval
+
+Remember: DO NOT write or edit any files yet. This is a read-only exploration and planning phase.`,
+  };
+}