fix(core): honor compaction disable settings

[TonyReg]

Issue for this PR

Fixes #32385

Type of change

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

What does this PR do?

This PR makes the compaction disable settings take effect in both config loading and V2 provider-overflow recovery.

• Applies OPENCODE_DISABLE_AUTOCOMPACT and OPENCODE_DISABLE_PRUNE as highest-priority core config overrides so environment variables win over lower-priority config files.
• Prevents compactAfterOverflow from auto-compacting when compaction.auto is disabled.
• Adds focused regressions covering the env overrides and the disabled provider-overflow recovery path.

This fixes the issue where users could set compaction.auto: false or OPENCODE_DISABLE_AUTOCOMPACT=true but still get automatic compaction after provider context overflow.

How did you verify your code works?

From packages/core:

• bun test test/session-compaction.test.ts
• bun test test/config-env.test.ts
• bun test test/session-runner.test.ts --test-name-pattern "provider context overflow"
• bun typecheck

Screenshots / recordings

Not applicable; this is a core/session behavior change with no UI changes.

Checklist

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

Reference: #32385

[github-actions]

Thanks for your contribution!

This PR doesn't have a linked issue. All PRs must reference an existing issue.

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

See CONTRIBUTING.md for details.

[github-actions]

The following comment was made by an LLM, it may be inaccurate:

The search found two potentially related PRs that address compaction configuration:

1. PR feat(session): add custom compaction thresholds along with prevention of continuous compaction #10123 - feat(session): add custom compaction thresholds along with prevention of continuous compaction

   • feat(session): add custom compaction thresholds along with prevention of continuous compaction #10123
   • Related: addresses compaction thresholds and prevention logic

2. PR fix(compaction): make compaction limits configurable and improve prompt detail retention #29324 - fix(compaction): make compaction limits configurable and improve prompt detail retention

   • fix(compaction): make compaction limits configurable and improve prompt detail retention #29324
   • Related: makes compaction limits configurable

These PRs may have overlapping concerns with the current PR #32864 regarding compaction configuration and auto-compaction behavior. You should review them to ensure there's no duplicate work, especially around config overrides and provider overflow recovery handling.

[github-actions]

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