Optimize large shell tool output

[bobrowadam]

• I added a entry in changelog under unreleased section.

Summary

• Optimize large shell output: When shell command output exceeds a configurable threshold (default: 1000 chars), write to a cache file (~/.cache/eca/{workspace-hash}/shell-output/) instead of returning inline. Reduces LLM context bloat for commands like find, git log, etc.
• Auto-allow reading cache files: Shell output cache files don't require additional read approval since the original command was already approved.

Details

• New config option: toolCall.shellCommand.outputFileThreshold (default: 1000)
• Response includes file path, size, exit code, and last 20 lines for context
• Graceful fallback to inline output if file write fails
• Works for both success (exit 0) and error (non-zero exit) cases