test(opencode): deflake file and tool timing

[Hona]

Why These Tests Started Flaking

• 2cbdf04ec made FileTime.read/get/assert/withLock async and instance-runtime backed, but the affected tests still treated FileTime.read(...) like a fire-and-forget synchronous boundary.
• 69381f6ae left File.init() as a background warmup, while the search tests were trying to use it as a readiness signal and then sleeping for 500ms.
• The file and tool tests also boot the full existing instance runtime, which pulls in provider auth and default plugin loading. In practice that unrelated bootstrap was consuming most of the 5s test budget before the file/edit assertions even ran.

What This PR Changes

• keep the production Effect/runtime architecture as-is
• make File.init() wait for the initial scan so callers and tests can use it as a real readiness boundary
• await FileTime.read(...) in the affected tests so they stop racing the async service boundary
• replace timestamp and lock-order sleeps with explicit fs mtimes and manual gates
• disable default plugins in test preload so unrelated provider/plugin bootstrap does not make file and tool tests time out

Testing

• bun typecheck
• bun test ./test/file/index.test.ts ./test/file/time.test.ts
• bun test ./test/tool/edit.test.ts ./test/tool/write.test.ts
• bun test ./test/tool/bash.test.ts ./test/plugin/auth-override.test.ts ./test/pty/pty-output-isolation.test.ts ./test/pty/pty-session.test.ts ./test/session/prompt.test.ts ./test/session/llm.test.ts
• repeated the previously flaky single tests for File.read() and EditTool creation three times each

[Copilot]

Pull request overview

This PR deflakes opencode’s file- and tool-related tests by turning previously timing-dependent assumptions into explicit async boundaries and deterministic filesystem timestamp manipulation, while also reducing unrelated bootstrap work during tests.

Changes:

• Await FileTime.read(...) in affected tool tests to avoid racing the async FileTime service boundary.
• Make File.init() a real readiness boundary by waiting for the initial scan (so search tests no longer rely on arbitrary sleeps).
• Reduce test runtime variance by disabling default plugins in the test preload and replacing sleep-based timing with explicit mtimes and manual gates.

Reviewed changes

Copilot reviewed 6 out of 6 changed files in this pull request and generated no comments.

Show a summary per file

File	Description
packages/opencode/test/tool/write.test.ts	Awaits FileTime.read so write tool tests don’t race async FileTime initialization.
packages/opencode/test/tool/edit.test.ts	Awaits FileTime.read and replaces sleep-based timestamp changes with explicit fs.utimes touches.
packages/opencode/test/preload.ts	Disables default plugins during tests to avoid unrelated bootstrap consuming the test time budget.
packages/opencode/test/file/time.test.ts	Replaces sleep-based flake-prone timing with explicit utimes and deterministic concurrency gates for lock tests.
packages/opencode/test/file/index.test.ts	Awaits File.init() instead of sleeping, using it as a proper readiness boundary.
packages/opencode/src/file/index.ts	Updates FileService.init to await the initial scan (kick()) so File.init() can be awaited as a readiness boundary.

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