docs: keep issues and PR descriptions concise and concrete

[teamleaderleo]

CMUX issues and PRs often bury the concrete change under implementation detail or accumulated status updates. Add a short STYLE.md for public writing, using recent CMUX descriptions as examples.

The guide covers leading with user/caller behavior, proportional detail, precise validation claims, current status, and decidable proposals. Link it from contributor guidance, agent instructions, and the PR template. Existing engineering and merge requirements are unchanged.

Validation: reviewed the Markdown and links; git diff --check passes. Documentation only, so no runtime tests or demo apply.

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Summary by cubic

Adds STYLE.md, a short public writing guide for CMUX issues, RFCs, and PRs, so descriptions lead with the concrete behavior change and base claims on precise evidence. Links it from the PR template, CONTRIBUTING.md, and CLAUDE.md, while keeping the existing contributor verification ladder in place. Documentation only; no runtime or review process changes.

^{Written for commit 3d88c82. Summary will update on new commits.}

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📥 Commits

Reviewing files that changed from the base of the PR and between 95fdfd7 and 3d88c82.

📒 Files selected for processing (4)

• .github/pull_request_template.md
• CLAUDE.md
• CONTRIBUTING.md
• STYLE.md

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[github-actions]

All contributors have signed the CLA ✍️ ✅
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[greptile-apps]

Confidence Score: 5/5

The documentation-only PR appears safe to merge, with no actionable issues identified.

Summary

Adds STYLE.md with concise writing guidance for issues, RFCs, PR descriptions, and progress updates.

• Emphasizes concrete behavior, proportional detail, precise validation claims, and current status.
• References the guide from contributor instructions, agent instructions, and the PR template while preserving existing engineering and approval requirements.
• Changes since the previous review only merge existing main-branch updates. No actionable new issues or repository-rule violations were identified.
• git diff --check passes. No runtime tests were run for this documentation-only PR.

_{Reviews (2) · Last reviewed commit: "Merge main into docs/public-writing-styl..."}