fix(doom-loop): improve wording of doom loop reminder

[laststylebender14]

fixes: #3247

Replace the vague doom loop reminder message with clearer, more actionable language that explicitly directs the agent to change approach rather than repeat the same tool call.

Before:

You appear to be stuck in a repetitive loop, having made N similar calls. This indicates you are not making progress. Please: 1. Reconsider your approach...

After:

You are stuck in a loop: you have made N identical or semantically equivalent tool calls without meaningful progress. For your next step, do NOT repeat the same tool call... You must choose one of these actions: 1. Use a different tool. 2. Use the same tool with materially different arguments... 3. Stop tool use and explain the blocker...