fix(agents): deny apply_patch for GPT models to prevent verification hangs (#2935)

GPT models (5.3-codex, 5.4, etc.) frequently hang when using apply_patch
due to verification loops. This adds:

1. Tool restriction: apply_patch is denied for GPT variants of
   Hephaestus, Sisyphus-Junior, and Sisyphus agents
2. Prompt guidance: GPT-specific prompts now explicitly instruct using
   edit/write tools instead of apply_patch
3. Removed the 'Always use apply_patch' instruction from
   sisyphus-junior/gpt-5-4.ts that contradicted the fix

The deny is model-conditional — Claude variants retain apply_patch
access since it works reliably there.

src/agents/sisyphus-junior/agent.ts

@@ -30,6 +30,7 @@ const MODE: AgentMode = "subagent"
 // Core tools that Sisyphus-Junior must NEVER have access to
 // Note: call_omo_agent is ALLOWED so subagents can spawn explore/librarian
 const BLOCKED_TOOLS = ["task"]
+const GPT_BLOCKED_TOOLS = ["task", "apply_patch"]
 
 export const SISYPHUS_JUNIOR_DEFAULTS = {
   model: "anthropic/claude-sonnet-4-6",
@@ -91,13 +92,14 @@ export function createSisyphusJuniorAgentWithOverrides(
 
   const promptAppend = override?.prompt_append
   const prompt = buildSisyphusJuniorPrompt(model, useTaskSystem, promptAppend)
+  const blockedTools = isGptModel(model) ? GPT_BLOCKED_TOOLS : BLOCKED_TOOLS
 
-  const baseRestrictions = createAgentToolRestrictions(BLOCKED_TOOLS)
+  const baseRestrictions = createAgentToolRestrictions(blockedTools)
 
   const userPermission = (override?.permission ?? {}) as Record<string, PermissionValue>
   const basePermission = baseRestrictions.permission
   const merged: Record<string, PermissionValue> = { ...userPermission }
-  for (const tool of BLOCKED_TOOLS) {
+  for (const tool of blockedTools) {
     merged[tool] = "deny"
   }
   merged.call_omo_agent = "allow"