Add workflow concurrency controls

[kitsuyui]

Summary

• Add top-level concurrency to test.yml and octocov.yml to cancel stale runs on the same branch/PR when a new push arrives
• Add top-level concurrency to binary-release.yml with cancel-in-progress limited to pull_request events so release builds are never cancelled

Verification

actionlint -shellcheck="" .github/workflows/test.yml .github/workflows/octocov.yml .github/workflows/binary-release.yml
# no output (all clear)

Trade-offs

• cancel-in-progress: true on test and octocov means any in-progress run on the same ref is cancelled when a new commit is pushed. This is the intended behaviour for PR iteration.
• cancel-in-progress: ${{ github.event_name == 'pull_request' }} on binary-release preserves running release builds while still cancelling stale PR builds.

[github-actions]

Code Metrics Report

	main (b742c4a)	#841 (7ed867d)	+/-
Coverage	71.8%	71.8%	0.0%
Code to Test Ratio	1:0.0	1:0.0	0.0
Test Execution Time	4m8s	5m21s	+1m13s

Details

  |                     | main (b742c4a) | #841 (7ed867d) |  +/-   |
  |---------------------|----------------|----------------|--------|
  | Coverage            |          71.8% |          71.8% |   0.0% |
  |   Files             |             18 |             18 |      0 |
  |   Lines             |           1949 |           1949 |      0 |
  |   Covered           |           1400 |           1400 |      0 |
  | Code to Test Ratio  |          1:0.0 |          1:0.0 |    0.0 |
  |   Code              |           2528 |           2528 |      0 |
  |   Test              |              0 |              0 |      0 |
- | Test Execution Time |           4m8s |          5m21s | +1m13s |

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Reported by octocov