Agent files use VS Code conventions instead of Primer conventions

[digitarald]

Problem

The 3 agent files in .github/agents/ (code-review-opus, code-review-gemini, code-review-codex) are copy-pasted VS Code codebase review instructions. They reference conventions that don't apply to Primer:

• Tabs vs spaces (Primer uses 2-space indent)
• I-prefixed interfaces (Primer doesn't use this)
• localize() / nls.localize() for strings (not applicable)
• Disposable lifecycle with _register() (not applicable)
• /common/, /browser/, /node/ layering rules (not applicable)
• Microsoft copyright headers (Primer uses MIT)

When AI uses these agents for code review, it enforces the wrong conventions.

Suggestion

Rewrite agent files to reference Primer's actual conventions from copilot-instructions.md:

• ESM everywhere, TypeScript strict mode
• Commands in src/commands/, services in src/services/, UI in src/ui/
• CommandResult<T> pattern, safeWriteFile(), output discipline (stdout=JSON, stderr=human)
• Vitest for tests, --json/--quiet flags on all commands
• Ink/React for TUI, Commander for CLI

Could also be a future Primer feature: primer generate agents that produces agent files matching detected repo conventions.