chore: guard lint-staged pre-commit hook - #1151

Summary

Make the pre-commit hook fail clearly when lint-staged is not installed locally.

Changes

• Guard the repository-local lint-staged executable before invocation.
• Direct contributors to run npm install when it is missing.
• Invoke the local executable directly, avoiding npx package resolution.
• Leave the existing lint-staged scope unchanged.

Testing / Verification

• sh -n .husky/pre-commit
• Isolated missing-binary scenario: exact guidance message and exit 1.
• Isolated present-binary scenario with npx unavailable: local binary
  invoked and exit 0.
• Isolated failing-binary scenario: exit status propagated.
• git diff --check

Related issue: #1077