fix(commit-lint): gate on pull_request events only (same pattern as jira-ticket-check)

[pdodgen-revparts]

Symptom

encodium/manage run 29053841708 — squash-merge of encodium/manage#7671 (DEVEX-1653 on_rt sweep) landed on main. The Pull Request Workflow re-fired on push:main, and commit-lint came back red:

• Squash commit subject: DEVEX-1653: thread on_rt input through deploy chain for Slack RT/Hotfix badge (taken from PR title per GitHub's default squash behavior)
• commitlint config-conventional: rejects — the subject starts with a Jira ticket ID, not a conventional type prefix (feat:, fix:, ci:, …)
• The failed check triggered the shared ci-failure-notify chain (DEVEX-1398) → #releases got a "check failed on main" alert that looks like a build failure but is actually cosmetic

Every squash-merge from any repo using the org PR-title convention (<TICKET-ID>: <terse description>) hits this. Manage is just the most visible because it merges frequently.

Fix

Add if: github.event_name == 'pull_request' to the commitlint job in the shared git-commit-lint.yaml. Same pattern I landed on jira-ticket-check.yaml in .github#144. On push:main the check skips (yellow), no false-negative fires.

Why not enforce commitlint on the squash-merge subject

Two paths considered:

• Fix the check (this PR): commit-lint on push:main adds no new signal — the PR's original commits were already commit-linted at PR time. The squash-merge subject is a mechanical concatenation from the PR title, not a human-authored commit. Re-checking it fires false-negatives whenever the org PR-title convention doesn't match commitlint's rules.
• Fix the convention: change PR-title convention org-wide to include a conventional type prefix (e.g. feat: DEVEX-1653 thread on_rt…). Breaks existing muscle memory + tooling, doesn't add value.

Path 1 is cheaper and matches the pattern we established for jira-ticket-check.

Verification

Next squash-merge to any repo using this workflow. The commit-lint job should render as skipped (yellow) on push:main, not failed (red). PR-time commit-lint on pull_request events is unchanged.

[cursor]

PR Summary

Low Risk
CI-only workflow condition change; PR commit linting is unchanged and push:main simply skips the job.

Overview
Stops commit-lint from running on push:main in the shared git-commit-lint.yaml reusable workflow by adding if: github.event_name == 'pull_request', matching the existing jira-ticket-check gate.

Squash-merge subjects use the org PR title (<TICKET-ID>: …), so commitlint fails on main even though PR-time lint already passed, which triggers false #releases CI failure alerts. The job still runs on pull requests; it is skipped (not failed) after merge.

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