style: improve plan deny preamble readability

Break the dense single-paragraph preamble into structured sections:
verdict, directive, and rules list. Easier for agents to parse.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

Author: backnotprop

packages/shared/feedback-templates.ts

@@ -14,7 +14,7 @@ export const planDenyFeedback = (
   feedback: string,
   toolName: string = "ExitPlanMode",
 ): string =>
-  `YOUR PLAN WAS NOT APPROVED. You MUST revise the plan to address ALL of the feedback below before calling ${toolName} again. Do not resubmit the same plan — use the Edit tool to make targeted changes to the plan file first. Do NOT change the plan title (first # heading) unless the user explicitly asks you to.\n\n${feedback || "Plan changes requested"}`;
+  `YOUR PLAN WAS NOT APPROVED.\n\nYou MUST revise the plan to address ALL of the feedback below before calling ${toolName} again.\n\nRules:\n- Use the Edit tool to make targeted changes to the plan — do not resubmit the same plan unchanged.\n- Do NOT change the plan title (first # heading) unless the user explicitly asks you to.\n\n${feedback || "Plan changes requested"}`;
 
 // ── Code review ──────────────────────────────────────────────────────