fix: cap long-lived queue and shell buffers

[jwcrystal]

Issue for this PR

Closes #20626

Type of change

• Bug fix
• New feature
• Refactor / code improvement
• Documentation

What does this PR do?

This fixes two long-running memory growth paths that can make a single OpenCode window consume very large amounts of memory over time.

First, it bounds the SSE queues used by the event routes and adds explicit close behavior so stalled or disconnected consumers do not keep accumulating buffered events in memory. It also preserves the final InstanceDisposed event before shutdown instead of dropping it.

Second, it stops bash and prompt subprocess output from growing unbounded in memory. Large bash output is now spilled to a truncation file while keeping the existing truncated / outputPath behavior, and prompt subprocess output is capped in memory as well. I also added a small follow-up guard so AsyncQueue.close() fails fast if called without a sentinel instead of leaving the queue in a half-closed state.

How did you verify your code works?

I tested the queue and bash-output regressions locally:

• bun test test/util/queue.test.ts
• bun test test/tool/bash.test.ts --filter "large-output spill-to-file|truncation"
• bun typecheck 2>&1 | grep -E "test/util/queue.test.ts|test/tool/bash.test.ts|src/util/queue.ts|src/server/routes/event.ts|src/server/routes/global.ts|src/tool/bash.ts|src/session/prompt.ts"

During push, the repo hook also ran successfully:

• bun turbo typecheck

I did not mark the full package test suite here because it is currently blocked by an existing @ai-sdk/provider-utils import error unrelated to this patch.

Screenshots / recordings

N/A

Checklist

• I have tested my changes locally
• I have not included unrelated changes in this PR

[github-actions]

Thanks for updating your PR! It now meets our contributing guidelines. 👍

[rekram1-node]

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