fix(test-runner): cap bun heap with --smol, env-gate scope:all, process-group kill on timeout

[zaxbysauce]

Summary

• �un --smol on every test run: both the dispatch path (src/lang/default-backend.ts) and legacy path (src/tools/test-runner.ts) now emit ['bun', '--smol', 'test', ...]. This caps bun's heap growth and eliminates OOM-driven OpenCode session crashes during broad test runs, matching the per-file CI pattern already used throughout the repo.

• scope: 'all' is now environment-gated: the agent-settable �llow_full_suite argument has been removed from TestRunnerArgs and the Zod schema. The only unlock is SWARM_ALLOW_FULL_SUITE=1 in the environment (CI/maintainer sessions only — not accessible via LLM tool call). The blocked-response message deliberately omits the env var name to prevent prompt-engineering.

• Process-group kill on timeout: �unSpawn gains an opt-in killProcessTree: true flag. When set (only by the test-runner), the Node spawn path uses detached: true and kills via process.kill(-pid) on POSIX or askkill /PID /T /F on Windows, reaping jest/vitest worker-pool descendants. The ~30 other �unSpawn callers are unaffected (opt-in only).

• Prose docs aligned: AGENTS.md §6, docs/engineering-invariants.md, and all agent-facing skill files updated to reflect the new gate. Agent-facing docs do not reveal the env var name.

Root cause

The tool crashed OpenCode sessions via OOM because (a) bun ran without --smol so heap grew unbounded across a 50-file batch, (b) �llow_full_suite: true was documented directly in the schema, teaching LLMs how to bypass the scope block, and (c) the schema alone enforced nothing — prose warnings in AGENTS.md failed repeatedly because nothing in the tool itself enforced safety.

Invariant audit

• 1 (plugin init): not touched — no changes to init path, startup subprocess, or withTimeout wrapping
• 2 (runtime portability): not touched — no new �un: imports outside bun-compat.ts; dist/index.js passes
  ode --input-type=module import OK; �undle-portability.test.ts / �undle-plugin-shape.test.ts unaffected
• 3 (subprocesses): touched — src/utils/bun-compat.ts: added killProcessTree opt-in; Node path uses detached: true + process.kill(-pid) (POSIX) / askkill /T (Windows); array-form spawn only; explicit cwd; stdin: 'ignore' inherited; timeout unchanged; all other ~30 callers unaffected (opt-in).
  ode scripts/repro-704.mjs passed all 3 timing assertions. dist import OK verified.
• 4 (.swarm containment): not touched — no new process.cwd() callers; no .swarm/ write path changes
• 5 (plan durability): not touched — no ledger, projection, or schema changes
• 6 (test_runner safety): touched — �llow_full_suite arg removed; SWARM_ALLOW_FULL_SUITE env gate added; --smol added to both bun command builders; killProcessTree: true added to test-runner spawn. Tests: est-runner.test.ts 115/0, est-runner-scope-cap.test.ts 14/2 (2 pre-existing), est-runner-dispatch-parity.test.ts 19/0, est-runner-history.test.ts 20/0, �un-compat.test.ts 8/0.
• 7 (test writing): touched — all modified test files use �un:test; no mock.module() calls in changed tests; os.tmpdir() + path.join() used throughout; env save/restore via try/finally in every new env-mutation test
• 8 (session state): not touched — no module-level globals changed
• 9 (guardrails/retry): not touched — no transient-error or circuit-breaker changes
• 10 (chat/system msg): not touched — no message hook changes
• 11 (tool registration): not touched — no new tools; est_runner schema narrowed (arg removed, not added)
• 12 (release/cache): not touched — version files untouched; release fragment at docs/releases/pending/test-runner-smol-env-gate-process-kill.md

Test plan

• sc --noEmit — exit 0, no type errors
• �iome ci . — 0 errors (17 pre-existing warnings in src/hooks/shell-write-detect.ts, verified on main)
• �un run build — exit 0; dist import OK (node ESM import)
• [x]
  ode scripts/repro-704.mjs — T1/T2/T3 all OK
• est-runner.test.ts — 115 pass / 4 skip / 0 fail
• est-runner-scope-cap.test.ts — 14 pass / 2 fail (pre-existing; baseline has 3 fail)
• est-runner-dispatch-parity.test.ts — 19 pass / 0 fail
• est-runner-history.test.ts — 20 pass / 0 fail
• �un-compat.test.ts — 8 pass / 0 fail
• ests/unit/services/** — 0 fail across all 34 service test files
• ests/unit/agents/** + ests/unit/hooks/** — 0 fail
• ests/unit/config — 1244/5 (5 pre-existing, identical count on origin/main)
• ests/unit/cli + ests/unit/commands — 1040/471 fail (identical on origin/main; pre-existing)

Pre-existing failures (not regressions)

All confirmed on origin/main baseline:

• est-runner-scope-cap.test.ts tests 9 and 11: expect 'scope_exceeded' but get 'error'; predate MAX_SAFE_SOURCE_FILES=1. My branch reduced pre-existing failures from 3 → 2.
• ests/unit/cli / ests/unit/commands: 471 failures matching origin/main exactly.
• ests/unit/config: 5 failures matching origin/main exactly.
• diagnostic-gating, doc-scan, phase-complete-lean-turbo-*, sast-and-cochanger-tools, ool-registration-conformance, update-task-status.gate-fix, pre-check-batch,
  egistration-smoke,
  epo-graph-codex-adversarial,
  epo-graph.adversarial: all in untouched files, all matching baseline.

[zaxbysauce]

@copilot resolve the merge conflicts in this pull request

[Copilot]

@copilot resolve the merge conflicts in this pull request

Resolved and pushed in commit bf1e76f: merged origin/main, fixed the two skill-doc conflicts, and completed the merge commit so the PR is no longer in a conflicted state.

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