[governance/repo-guard] Clarify source-generated closure rule

[konard]

Fixes #291

Summary

• Clarifies docs/pmm_transformation_rules.md so required source -> generated closure is distinct from forbidden mixed generated changes.
• Keeps regeneration PRs isolated by default while allowing minimal mechanically required generated sync when it directly follows an allowed canonical source diff.
• Adds reviewer semantics for checking that generated diffs are mechanically explained and not disguised independent churn.

Surface Contract

• Changed files: docs/pmm_transformation_rules.md only
• New files: 0
• New markdown files: 0
• Code/test/example/demo surface touched: no
• Generated surface touched: no
• Diff size: 10 insertions, 1 deletion

Verification

• bash scripts/check-docs-consistency.sh
• bash scripts/check-repo-guard-rollout.sh
• bash scripts/check-file-size.sh
• git diff --check

Notes

No automated reproducing test was added because this issue explicitly forbids tests/** and asks for a governance wording update only.

[konard]

Solution summary

Implemented and finalized PR 292: #292

Changed only docs/pmm_transformation_rules.md. The rule now explicitly separates forbidden generated-surface mixing from minimal mechanically required source -> generated closure, and adds reviewer guidance for validating that closure.

Verification run locally:

• bash scripts/check-docs-consistency.sh
• bash scripts/check-repo-guard-rollout.sh
• bash scripts/check-file-size.sh
• git diff --check

Branch was pushed to issue-291-27288c594291, PR title/body were updated, and the PR is marked ready for review. GitHub Actions on the fork show Docs Consistency passing for commit 7e6f0dc.

No automated test was added because this issue explicitly forbids tests/** and is limited to governance wording.

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[konard]

🤖 Solution Draft Log

This log file contains the complete execution trace of the AI solution draft process.

💰 Cost estimation:

• Model: gpt-5.4
• Provider: OpenAI
• Public pricing estimate: unknown
• Token usage: 23,560 input, 3,769 output, 468,736 cache read

📊 Context and tokens usage:

Total: (23.6K + 468.7K cached) input tokens, 3.8K output tokens

🤖 Models used:

• Tool: OpenAI Codex
• Requested: gpt-5.4
• Model: GPT-5.4 (gpt-5.4)

📎 Log file uploaded as Gist (5256KB)

• View complete solution draft log

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[konard]

✅ Ready to merge

This pull request is now ready to be merged:

• All CI checks have passed
• No merge conflicts
• No pending changes

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