Decide when a summary agent should stay quiet

An agent writes a summary for every pull request. A fluent wrong summary is worse than none, because it steers reviewers away from the code, so the agent has to know when to hold back.

Write pr_summary_decision(files_changed, lines_changed, generated_files, distinct_areas, has_linked_ticket): the rule your agent follows for each pull request.

• files_changed, lines_changed (int): the size of the diff.
• generated_files (int): how many of the changed files are generated (lockfiles, snapshots, build output).
• distinct_areas (int): how many unrelated parts of the codebase the change touches.
• has_linked_ticket (bool): the pull request links a ticket that explains why.

It returns one of the values in the rules below. Apply them in order. The first one that matches decides:

1. files_changed or lines_changed is 0 or less: "withhold-no-evidence".
2. More than 40 files, or more than 800 lines: "withhold-oversized".
3. Half the files or more are generated (generated_files * 2 >= files_changed): "withhold-generated".
4. 4 or more distinct areas: "withhold-mixed".
5. A linked ticket, at most 1 area and at most 200 lines: "post-high".
6. A linked ticket, or else both at most 2 areas and at most 400 lines: "post-medium".
7. Otherwise: "post-low".