feat: add workflow rules to AGENTS.md for test ordering, template usage, and self-improvement flow

[eskenazit]

Related Issue

No issue — improvements derived from corrections during #243 workflow.

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What does this PR do?

Adds four rules to AGENTS.md based on corrections made during the bug fix workflow for #243:

• Test/fix ordering (Bug Workflow Step 3): explicit phase separation — write tests in src/test first, confirm they fail, only then fix src/main
• Template usage (Contribution Workflow): always read .github/ISSUE_TEMPLATE/ and PULL_REQUEST_TEMPLATE.md before creating issues or PRs
• Self-improvement flow: note corrections immediately but resume the workflow — propose rule updates only at end (Bug Workflow Step 4 + Contribution Workflow end-of-list)
• AGENTS.md commit prefix: improvements are feat:, not chore:

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Tests

No tests — documentation-only change.

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Checklist

• CI is green (build, tests, schema validation, security scans)
• Rebased on latest main
• Small and focused — one concern per PR
• Commit messages follow Conventional Commits

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Agent Context (optional)

agent_name: GitHub Copilot
llm: Claude Opus 4.6
tool: VS Code Chat
confidence: high
source_event: '#243 workflow corrections'
discovery_method: user_report
review_focus: AGENTS.md