fix(core): handle aborted overflow compaction

[cwj2001]

Issue for this PR

Fixes #27924

Type of change

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

What does this PR do?

Handles aborted overflow recovery compaction without re-entering the compaction loop.

When the provider reports context overflow before assistant output, OpenCode tries to summarize and retry once. If that summary stream aborts or dies with a non-interrupt failure, this PR treats the summary as failed and persists the original provider overflow as the assistant error.

Real user/session interrupts still propagate as interrupts.

How did you verify your code works?

• bun test test/session-runner.test.ts --test-name-pattern "publishes the original overflow when recovery summarization aborts" from packages/core
• bun test test/session-runner.test.ts --test-name-pattern "overflow" from packages/core
• bun typecheck from packages/core
• Push hook ran bun turbo typecheck: 29 successful, 29 total

Screenshots / recordings

N/A. Core session recovery fix.

Checklist

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

[github-actions]

Thanks for your contribution!

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Please:

1. Open an issue describing the bug/feature (if one doesn't exist)
2. Add Fixes #<number> or Closes #<number> to this PR description

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