fix: run feature validation during fix

[rohitjavvadi]

Fixes #23

Summary

• make clawpatch fix use feature-aware validation commands in dry-run and real execution
• preserve the intended validation order: formatter, targeted feature tests, typecheck, lint, broader tests
• ignore empty feature test commands and deduplicate repeated validation commands
• add workflow regression tests for dry-run output, failed targeted validation, empty-command filtering, dedupe, and command ordering

Why

clawpatch show already surfaced feature-specific validation commands, but clawpatch fix only ran global configured commands. A fix could therefore be recorded as applied without running the targeted test attached to that feature.

Validation

• corepack pnpm typecheck
• corepack pnpm lint
• corepack pnpm format:check
• corepack pnpm test
• corepack pnpm build
• Claude Review approved the final diff
• three independent edge-case/robustness reviews found no blocking issues