feat(validation): render named message arguments #10

Summary

• Add static and computed named arguments to typed rule messages.
• Expose bounds and measured values from built-in checks to caller templates.
• Render each template once so inserted values remain literal and unused factories are not called.

Validation

• pudu check $(rg --files src test -g '*.pudu')
• pudu fmt --check src test
• pudu lint src test
• pudu test test — 14 suites, 96 assertions

Closes #9