fix: expand SHA regex to support SHA-256 (64-char) commit hashes

[yaananth]

Summary

Update input-helper.ts to recognize both 40-char (SHA-1) and 64-char (SHA-256) hex strings as commit SHAs. Rebuild dist/index.js.

Changes

• src/input-helper.ts: Update regex from /^[0-9a-fA-F]{40}$/ to /^(?:[0-9a-fA-F]{40}|[0-9a-fA-F]{64})$/
• dist/index.js: Rebuilt bundle

Validation

• Build passes (npm run build)
• 8 test suites, 96 tests pass (npm test)

Context

• Parent epic: SHA-256 Support for Git Repositories

---

Automated by project-board-agents-plugin via /project-board-agents:lead
Board: https://github.com/orgs/github/projects/24272/views/1
Item: [P0] Fix SHA-1 regex in actions/checkout input-helper.ts
Run: sha256-p0-checkout-00050

[salmanmkc]

the existing test at __test__/input-helper.test.ts line 129–134 only covers 40-char SHA inputs, can we add one for 64-char SHAs to correctly identity it as a commit and that it's not treated as a branch. e.g.:

it('sets ref to empty when explicit sha-256', async () => {
  inputs.ref = '1111111111222222222233333333334444444444555555555566666666667777'
  const settings = await inputHelper.getInputs()
  expect(settings.ref).toBeFalsy()
  expect(settings.commit).toBe('1111111111222222222233333333334444444444555555555566666666667777')
})

[salmanmkc]

I think we can combine this PR with this PR: #2414, what do you think? I think the automation created two PRs, since I had made three issues before for checkout sha256 work, however it somehow managed to combine two into #2414 but didn't combine it with this PR.