feat(test-impact): classify infrastructure failures separately

[Copilot]

Summary

• Adds infrastructure_failure classification for OOM, process termination, network, timeout, and exit-code-137 failure text.
• Narrows the Killed matcher so domain assertion text such as expected process to be killed still follows normal regression classification.
• Includes focused classifier/barrel coverage, a pending release fragment, and rebuilt tracked dist/ artifacts.

Invariant audit

• 1 (plugin init): not touched - no plugin-init code changed; node scripts/repro-704.mjs printed OK for T1/T2/T3, then the process did not exit and the single identified node PID was stopped.
• 2 (runtime portability): touched - bun run build, bun test tests/unit/build/bundle-portability.test.ts tests/unit/build/bundle-plugin-shape.test.ts tests/unit/build/bundle-node-load.test.ts, node --input-type=module -e "await import('./dist/index.js'); console.log('dist import OK')", and post-commit git diff --exit-code -- dist passed.
• 3 (subprocesses): not touched - no source subprocess code changed.
• 4 (.swarm containment): not touched - no .swarm path or working-directory logic changed.
• 5 (plan durability): not touched - no plan ledger/projection code changed.
• 6 (test_runner safety): not touched - repo validation used shell commands, not the OpenCode test_runner tool.
• 7 (test writing): touched - loaded .opencode/skills/writing-tests/SKILL.md; added a bun:test regression in the existing classifier test file with no mocks.
• 8 (session state): not touched - no session/global state changed.
• 9 (guardrails/retry): not touched - no guardrail/retry logic changed.
• 10 (chat/system msg): not touched - no chat/system-message hooks changed.
• 11 (tool registration): not touched - no tool map or registration changed; barrel type export coverage was updated only for the classifier type surface.
• 12 (release/cache): touched - added docs/releases/pending/failure-classifier-infrastructure-failure.md; no cache/version files changed.

Test plan

• bun test src/test-impact/__tests__/failure-classifier.test.ts src/test-impact/__tests__/failure-classifier.adversarial.test.ts src/tools/__tests__/barrel-exports.test.ts
• Runtime probes: assertion text containing killed returns new_regression; bare Killed returns infrastructure_failure
• bun run typecheck
• bunx biome ci src/test-impact/failure-classifier.ts src/test-impact/__tests__/failure-classifier.test.ts src/tools/__tests__/barrel-exports.test.ts docs/releases/pending/failure-classifier-infrastructure-failure.md
• bunx biome ci . exited 0 with 10 warning-only findings in unrelated files
• bun run build
• git diff --exit-code -- dist after rebuild
• node --input-type=module -e "await import('./dist/index.js'); console.log('dist import OK')"
• bun test tests/unit/build/bundle-portability.test.ts tests/unit/build/bundle-plugin-shape.test.ts tests/unit/build/bundle-node-load.test.ts
• git diff --check

Validation notes

• Broader src/tools/__tests__/test-runner-history.test.ts still has an unrelated existing assertion mismatch for the scope "all" error message.
• node scripts/repro-704.mjs printed OK for all three documented scenarios but did not exit; the single identified node process was stopped. This PR does not change plugin init code.

[zaxbysauce]

@copilot review this PR

[Copilot]

@copilot review this PR

Reviewed and addressed follow-up risks in 2e5f4ea. I tightened infrastructure matching context, added assertion-error guard handling in the classifier, and validated with targeted classifier + bundle portability tests (all passing).