[No QA] Scope HelpDot docs review to PR opened/ready_for_review only

[MelvinBot]

Explanation of Change

The HelpDot QA review (/review-helpdot-pr, the docs step in the "PR Reviews with Claude Code" workflow) previously ran on both pull_request_target (PR opened / ready_for_review) and pull_request_review: submitted — meaning it re-ran in full every time a Contributor+ approved the PR. Each run re-reviews all changed docs files from scratch with no deduplication, so help-site PRs that went through multiple approval cycles accumulated several rounds of bot review comments (e.g. #90535 got a fresh round after each approval).

This change adds && github.event_name == 'pull_request_target' to the "Run Claude Code (docs)" step's if condition so the docs review only runs once at submission (opened / ready_for_review). The code-review step (src/**) is intentionally left unchanged and still re-runs on Contributor+ approval.

- name: Run Claude Code (docs)
  if: steps.set-authorized.outputs.IS_AUTHORIZED == 'true' && steps.filter.outputs.docs == 'true' && github.event_name == 'pull_request_target'

Fixed Issues

$ https://github.com/Expensify/Expensify/issues/643291
PROPOSAL: https://github.com/Expensify/Expensify/issues/643291#issuecomment-4589848893

Tests

CI-only workflow change — no app runtime behavior is affected. Validation performed:

1. Confirmed the diff is a single-line change to the if condition of the "Run Claude Code (docs)" step.
2. Confirmed github.event_name == 'pull_request_target' is already used as a valid expression elsewhere in the same workflow (lines 47 and 51).
3. After merge, behavior can be verified by: (a) opening a docs PR → docs QA review runs once; (b) having a Contributor+ approve a docs PR → docs QA review does not re-run.

• Verify that no errors appear in the JS console

Offline tests

N/A — CI workflow change.

QA Steps

[No QA] — this is a CI/workflow configuration change with no user-facing impact.

• Verify that no errors appear in the JS console

PR Author Checklist

• I linked the correct issue in the ### Fixed Issues section above
• I wrote clear testing steps that cover the changes made in this PR
• I verified there are no console errors
• If the main branch was merged into this PR after a review, I tested again and verified the outcome was still expected according to the Test steps.

Screenshots/Videos

N/A — CI workflow change, no UI impact.