change default values, improve prompt building

[radetsky]

Added

• max_tokens input in GitHub Action to override max tokens per LLM request per workflow run.
• timeout input in GitHub Action to override LLM request timeout per workflow run.
• LLM_MAX_RESPONSE_TOKENS environment variable to control max tokens in LLM response (default: 16384).
• llm.max_response_tokens config key (default: 16384).

Changed

• Default llm.timeout increased from 180 to 600 seconds to accommodate slow providers and large diffs with chunking.
• Default max_tokens_per_request increased to 32768 (see v0.1.3 notes).
• LLM requests now use system + user message roles instead of a single user message, giving reviewer instructions higher priority in the model's context window.
• max_tokens is now explicitly passed in every LLM API call, preventing unbounded response generation.

[github-actions]

⚠️ LLM Code Review

Status: Model Unavailable (static analysis used)

Category	Count
Critical Issues	0
Warnings	1
Suggestions	0

Warnings

• ⚠️ 🔴 LLM model unavailable: Error code: 401 - {'detail': 'Your session has expired or the token is invalid. Please sign in again.'}

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