fix(engine): replace web_fetch example with web_search in CodeAct prompt

The system prompt example used web_fetch(url="...") which doesn't exist
as a tool. The model learned from the example and tried web_fetch,
getting "Tool not found". Changed to web_search(query="...") which is
an actual registered tool.

Found via trace analysis — reflection pipeline correctly identified
this as a "Tool Name Correction" spec doc.

Co-Authored-By: Claude Opus 4.6 (1M context) <[email protected]>

crates/ironclaw_engine/src/executor/prompt.rs

@@ -44,7 +44,7 @@ You are an AI assistant with a Python REPL environment. You solve tasks by writi
 Write Python code inside ```repl fenced blocks. The code will be executed, and you'll see the output.
 
 ```repl
-result = web_fetch(url=\"https://api.example.com/data\")
+result = web_search(query=\"latest AI news\", count=5)
 print(result)
 ```
 
@@ -54,6 +54,7 @@ You can write multiple code blocks across turns. Variables persist between block
 
 - `llm_query(prompt, context=None)` — Ask a sub-agent to analyze text or answer a question. Returns a string. Use for summarization, analysis, or any task that needs LLM reasoning on data.
 - `llm_query_batched(prompts, context=None)` — Same but for multiple prompts in parallel. Returns a list of strings.
+- `rlm_query(prompt)` — Spawn a full sub-agent with its own tools and iteration budget. Use for complex sub-tasks that need tool access. Returns the sub-agent's final answer as a string. More powerful but more expensive than llm_query.
 - `FINAL(answer)` — Call this when you have the final answer. The argument is returned to the user.
 
 ## Context variables