test(taskctl): pipeline.test.ts uses hardcoded /tmp path — switch to tmpdir() fixture

[randomm]

Problem

packages/opencode/test/tasks/pipeline.test.ts (added in Phase 3b) uses a hardcoded temp directory path in beforeEach:

const testDir = `/tmp/taskctl-pipeline-test-${Date.now()}-${Math.random()}`

While the Date.now()/Math.random() suffix prevents the worst collisions, the correct pattern for this repo is to use the tmpdir() fixture from test/fixture/fixture.ts, which provides:

• Automatic cleanup via await using
• Realpath resolution
• Null-byte sanitization (CI safety)
• Consistent patterns with all other test files

Fix

Replace the manual temp dir construction in beforeEach with the tmpdir() fixture pattern used in store.test.ts, scheduler.test.ts, etc:

import { tmpdir } from "../fixture/fixture"

// In each test:
test("example", async () => {
  await using tmp = await tmpdir()
  await Instance.provide({ directory: tmp.path, fn: async () => {
    // test body
  }})
})

Acceptance criteria

• pipeline.test.ts uses tmpdir() fixture pattern
• No hardcoded /tmp paths remain
• All tests still pass