self-development: have workers self-review and squash commits before signaling ready

[kelos-bot]

What type of PR is this?

/kind cleanup

What this PR does / why we need it:

Updates the kelos-workers and kelos-pr-responder prompts to add two recurring asks from the last week of /kelos pick-up review feedback:

1. Self-review locally before requesting /review. The agent should re-read git diff origin/main...HEAD, run make verify and make test, and fix obvious issues itself before asking the reviewer agent to look.
2. Squash commits before signaling the PR is ready. A new final step rebases-then-squashes all branch commits into a single commit and force-pushes — only when there are 2+ commits since the merge base.

Motivating review feedback from PRs merged/active this week (all from @gjkim42):

• PR self-development: workers request review via /kelos review #1204 (self-development: workers request review via /kelos review): "You still need to review your coee locally in addition to the kelos review. Then squash commits." — covers both asks in one comment.
• PR Drop removed --enable skills flag from codex entrypoint #1175 (multiple comments): "/kelos pick-up\nSquash commits after the work" and "/kelos pick-up\nSquash commits then".
• PR Drop ValidArgsFunction from 'kelos create workspace' #1180: "/kelos pick-up\nAnd squash commits."
• PR Stream agent output through kelos-capture instead of writing to /tmp #1189: "/kelos pick-up\nAnd squash commits".
• PR self-development: scope kelos-planner, kelos-reviewer, and kelos-api-reviewer with commentOn #1205: "/kelos pick-up\nthen squash commits".
• Plus similar comments on PRs Fix CLI SOURCE column for GitHub/Slack TaskSpawners #1168, docs: refresh model ID examples and document shorthand format #1177, self-development: document modern webhook filter fields in README #1178, Wire Antigravity CLI as a first-class agent type #1194.

The existing kelos-squash-commits TaskSpawner stays as the explicit /kelos squash-commits escape hatch — this change just makes squashing the default for normal worker/responder runs so maintainers don't have to ask each time.

Which issue(s) this PR is related to:

N/A

Special notes for your reviewer:

• The squash step lives after the CI-check step (9 / 9a / 8b). The note "the squash does not change the tree, so CI results remain valid" tells the agent not to re-wait for checks after the force-push.
• Skipped when there is only one commit since the merge base, to avoid pointless force-pushes.

Does this PR introduce a user-facing change?

NONE

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Summary by cubic

Have kelos-workers and kelos-pr-responder self-review changes and squash commits before marking a PR ready. This reduces reviewer churn and keeps PR history clean.

• Refactors
  • Add local self-review before /review (read git diff origin/main...HEAD, run make verify and make test).
  • Add final squash step: make a single commit; skip if only one since merge base; git push --force-with-lease.
  • Place squashing after CI; tree is unchanged, so no need to re-wait checks.

^{Written for commit 8498cda. Summary will update on new commits. Review in cubic}

[gjkim42]

Should not always squash commits