Add a policy on fixing things that aren't broken

[IntegratedQuantum]

see #1925 (comment)

[AngelLITG]

Policy: “Fixing Things That Aren’t Broken”

Goal:
Keep PR focus on user-visible value, reduce churn, and prevent regressions from “preference” or “style-only” changes.

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Scope

Covers all PRs that change behavior or platform tooling without:

• A confirmed bug report, or
• A measurable user benefit (compatibility, security, performance, or maintainability).

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Definitions

• Broken: Feature fails on any supported platform/config or contradicts documented behavior.
• Unbroken: Works as documented on all supported targets.
• Net Value: Evidence-backed improvement (compatibility breadth, security, perf, maintainability).

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Acceptance Criteria

A PR that adjusts a non-broken area must satisfy at least one:

1. Compatibility Proof
   Expands support (e.g., works on more distros/OSes) with evidence (commands, versions, CI matrix, or user reports).

2. Security Improvement
   Fixes or mitigates a known vulnerability (CVE, advisory, threat model, etc.).

3. Performance Benefit
   Shows measurable wins (benchmarks, before/after numbers) with no regressions.

4. Maintenance Reduction
   Simplifies codepath, removes dead code, reduces deps, or aligns with a widely adopted, documented standard.

If none apply → prefer Issue discussion first; PR may be closed as Low Value / No Evidence.

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Evidence Checklist (required in PR description)

• Problem statement: Broken? If yes, include repro (cmds, env, versions).
• Supported platforms: List what improves or remains equal (e.g., Ubuntu 24/25, Fedora 41, Arch, macOS 14).
• Proof: Logs/commands/links (e.g., command -V xdg-open, CI job artifacts).
• Risk analysis: Behavior changes? Fallbacks? Edge cases?
• Tests/CI: Added/updated tests or CI matrix entries.
• Roll-back plan: How to revert if issues appear.

Example (from the xdg-open case):

• Problem: open unavailable by default on Ubuntu 24.04, Fedora 41, Arch → feature broken.
• Evidence: command -V open → not found; command -V xdg-open → present.
• Satisfies Compatibility Proof.

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Review Process

1. Labels:

   • needs-evidence – Missing proof
   • compat-improvement – Expands platform support
   • perf-claim – Claims perf change
   • maintenance – Refactor/cleanup only
   • risk-behavior-change – May affect users

2. Decision Tree:

   • Repro of broken behavior on a supported target → Bugfix path
   • No repro but clear value + evidence → Value PR path
   • No repro & no evidence → Request evidence or close

3. Approvals:

   • Bugfix with repro → 1 reviewer
   • Value PR (behavioral change) → 2 reviewers or 1 reviewer + passing CI matrix

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Exceptions

Fast-track (skip debate):

• Critical security fixes
• CI/build breakages
• Docs/comment-only changes

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Templates

PR Template Snippet

### Problem Statement
Is something broken? If yes, include repro (env, versions, commands):

### Value Justification (pick ≥1)
- [ ] Compatibility (with evidence)
- [ ] Security (CVE/advisory)
- [ ] Performance (before/after benchmarks)
- [ ] Maintenance (lines removed / complexity reduced)

### Platforms Tested
(e.g., Ubuntu 24.04, Fedora 41, Arch, macOS 14)

### Risk & Behavior Changes
Describe fallbacks, edge cases, and user impact.

### Tests/CI
What changed or was added?

### Roll-Back Plan
How to revert if issues arise?