Fix: Remove duplicate CI runs by removing pull_request trigger (fixes #133)

[wkoszek]

Summary

Remove pull_request trigger from build workflow to prevent duplicate CI runs. CI was running twice for PR pushes (once for push, once for pull_request event).

Problem

When pushing to a PR branch:

1. Push event triggers build workflow ✅
2. Pull request event also triggers build workflow ❌ (duplicate)

Result: Same commit tested twice, wasting CI resources

Solution

Remove pull_request trigger, keep only push trigger for all branches.

Behavior After Fix

• Branch push: CI runs once ✅
• PR creation: No additional run (already ran on push) ✅
• PR update: No additional run (already ran on push) ✅
• Merge to main: CI runs once, creates release if feat/fix commits ✅
• Manual trigger: Still works via workflow_dispatch ✅

Changes

• Remove pull_request: from workflow triggers
• Keep push: branches: ['**'] for all branches
• Keep workflow_dispatch: for manual runs
• Release steps remain conditional on github.ref == 'refs/heads/main'

Fixes #133

[claude]

Correct approach. Removing pull_request trigger eliminates duplicate CI runs.

Verify: Check that PR checks still display correctly on GitHub. Some repos need pull_request for check status reporting on PR pages, but with push on all branches ('**'), checks should still appear since they run on the PR's head branch.

Edge case: External forks won't trigger CI on push (they can't push to your repo). If you accept external contributions, you'll need pull_request_target with appropriate safety controls. If not accepting external PRs, this is fine.

Ship it.