feat(mold): add tcr (test && commit || revert) rule mold

[kriscoleman]

Create a new ailloy mold that provides a single TCR (Test && Commit || Revert) rule based on Kent Beck's TCR workflow. The mold should be AI platform agnostic, outputting the rule in the appropriate format for each target:

• Claude Code: .claude/rules/tcr.md (Claude rule file)
• GitHub Copilot: .github/copilot-instructions.md (see Copilot custom instructions)
• OpenAI Codex / GPT: AGENTS.md (see Codex AGENTS.md guide)

The mold should be scaffolded in /tmp/ for now and moved into its own repository later.

Acceptance Criteria

• Scaffold a new mold in /tmp/tcr-mold/ using ailloy mold new (or manually)
• mold.yaml with proper metadata (name: tcr, version: 0.1.0, description, author)
• Single rule template file containing TCR workflow instructions (platform-agnostic markdown)
• flux.yaml with configurable variables:
  • test_command (e.g., go test ./..., bun test, npm test) - the command to run tests
  • test_watch_command (optional) - watch mode variant
  • test_file_command (optional) - single file test variant
  • project_name (optional) - project identifier
• flux.yaml output mapping defaults to Claude target (.claude/rules/)
• Rule content covers all TCR principles: TDD-first, small increments, run tests constantly, embrace reversion
• Rule content uses flux template variables for test commands (not hardcoded to any specific runner)
• Rule is structured as practical guidelines an AI agent can follow, not just documentation
• Mold validates cleanly with ailloy temper
• Mold renders correctly with ailloy forge for default (Claude) target

Notes

• The rule content should be adapted from the attached example but made generic using flux variables for test commands
• For Claude, the output target is .claude/rules/ which maps to a Claude rule file
• For Copilot, the same content could be output to .github/copilot-instructions.md or .github/instructions/tcr.instructions.md
• For Codex/GPT, the content could be output to AGENTS.md at project root
• The flux.yaml output: mapping handles the platform targeting — users change the output destination based on their AI tool
• This is a single-rule mold (no commands, no skills, no workflows) — just the rule template and metadata
• Reference: Kent Beck's TCR article: https://medium.com/@kentbeck_7670/test-commit-revert-870bbd756864