ci: run the build check on merge_group

[os-support-ai]

Fixes#76

Problem

The repo's merge queue is armed with build as a required check today. .github/workflows/ci.yml's on: block only listened for push and pull_request, so it never produces a check run on the temporary merge-group ref a queued PR is validated against — every queued PR waits forever for a required check that never starts.

Fix

Add the merge_group: trigger to ci.yml's on: block. Minimal diff — one line, nothing else touched:

 on:
push:
branches: [main]
pull_request:
branches: [main]
+ merge_group:
jobs:
build:

deploy-docs.yml and translations.yml are unchanged (out of scope per the card). The inert test turbo task is a separate, already-filed finding (#72) and is untouched here.

Self-landing property

This PR can land through the merge queue itself: a merge-group run executes the workflow as defined at the merge-group ref, which includes this PR's own merge_group: addition — so once queued, this change produces the build check that then lets it merge.

Validation

• python3 -c "import yaml; d=yaml.safe_load(open('.github/workflows/ci.yml')); print(d[True])" → {'push': {'branches': ['main']}, 'pull_request': {'branches': ['main']}, 'merge_group': None} (PyYAML 1.1 parses the on: key as boolean True; this is a known quirk, not an error). Parses cleanly, merge_group present as a bare trigger alongside the existing two.
• yamllint not available in this environment; relied on the YAML parse above plus manual diff review.
• Diff reviewed: exactly the merge_group: line added, no other changes.

Generated by Claude Code

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Generated by Claude Code