bug(test): `prependEnvVars` import fails under concurrent test runs, blocking all local pushes

[namastex888]

Symptom

`bun run check` (which runs `bun test` across all 181 test files in parallel) consistently fails with ~10 failures caused by a single cascading module-load error:

```
SyntaxError: Export named 'prependEnvVars' not found in module '.../src/lib/tmux-wrapper.ts'.
at link (unknown:1:11)
at linkAndEvaluateModule (unknown:1:11)
at loadAndEvaluateModule (unknown:2:1)
```

Impact

• Local pushes via husky pre-push hook are blocked for every contributor
• The hook runs `bun run check` on every push; the check reports 3106 pass / 11 fail / 7 errors
• Agents cannot open PRs autonomously because they cannot bypass the hook (`--no-verify` forbidden by agent bible)

Affected test files (all fail to load)

• `src/lib/tests/transport-aware-liveness.test.ts` (2 tests fail)
• `src/lib/tests/edge-cases-stability.test.ts`
• `src/tests/tui-spawn-dx.integration.test.ts`
• `src/term-commands/agents.test.ts`
• `src/term-commands/tests/dispatch-slug.test.ts`
• `src/term-commands/tests/agents-resume.test.ts`
• `src/term-commands/state.test.ts`
• `src/term-commands/dispatch.test.ts`

Also-reported (unrelated)

• `(fail) 7.3 Security > slug validation covers all path traversal vectors` — separate issue
• `(fail) pen-test: listen-bomb — NOTIFY flood back-pressure response` — separate flaky

Investigation

• `prependEnvVars` is correctly exported from `src/lib/tmux-wrapper.ts:71`
• Running `bun test src/lib/tests/transport-aware-liveness.test.ts` in isolation: 10 pass, 0 fail
• Running `bun test` with all files: same test fails with module-load error
• The `1 | })` / `2 | {` marker in the trace suggests the file content is being corrupted during concurrent module load — likely a Bun runtime bug or a circular-import/module-cache race

Proposed mitigation

Possible short-term fixes:

1. Add an explicit import barrel so modules load serially at the start of each test file.
2. Mark the affected tests `bun.serial` (or isolate them into their own `bun test` invocation in the pre-push script).
3. File a Bun issue with a minimal reproducer and ship a workaround pending the upstream fix.

Blocker

This gate blocks every non-trivial PR. Because `bun run check` is the pre-push gate, the flake has the same severity as a permanently-red CI.

[namastex888]

Resolved by 2dcfda6e fix(test): add prependEnvVars to tmux-wrapper mocks landed in dev. Closed via housekeeping triage 2026-04-21.