feat(pre-commit): add husky pre-commit scan for staged files (issue#257)

[dDevAhmed]

Summary

• Adds a committed Husky pre-commit hook that runs GasGuard scans on staged smart-contract files so issues are detected before commits.

What changed

• Files added: pre-commit-scan.js — staged-file scanner that filters .sol, .vy, .rs and invokes the CLI for each file. See pre-commit-scan.js.
• Files added: pre-commit — committed Husky hook that runs the staged-file scanner. See pre-commit.
• Files modified: package.json — adds "prepare": "husky install" script and husky devDependency so hooks are installed on pnpm install. See package.json.

Why

• Prevent gas/regression issues from being committed by scanning staged contract files at commit time.
• Minimal, developer-local protection that does not change runtime behavior or CI policies.

Testing performed

• Ran node scripts/pre-commit-scan.js locally; it exits cleanly when no staged scannable files exist.
• Created branch feature/issue-257-husky-precommit, committed only the three relevant files and pushed the branch.
• Suggested local test flow:
  • Install deps (sets up Husky):
    • pnpm install
  • Make executable (if required):
    • chmod +x .husky/pre-commit
  • Stage a scannable file and commit:
    • git add path/to/contract.sol
    • git commit -m "test pre-commit hook"

Risks considered

• Hook invokes the TypeScript CLI via ts-node/register; dev dependencies must be installed for the hook to run. This is documented in the test steps.
• Running one scan per staged file may be slower with many staged files. This is intentionally minimal; can be optimized to batch-scan if desired.

Edge cases handled

• If there are no staged scannable files, the hook exits successfully and allows the commit.
• If a scan fails for a staged file, the commit is blocked (exit code 1), preventing bad commits.

Remediation / follow-ups (optional)

• Batch staged files into a single scanner invocation for performance.
• Add a GitHub Action to run the same scan on pushes/PRs for server-side enforcement.
• Replace ts-node invocation with a built gasguard binary for environments that prefer not to rely on devDependencies.

Branch

• feature/issue-257-husky-precommit

Closes #257

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