fix(session): add fallback retry handling and harden pre-push bun path

[C24-AK]

Issue for this PR

Not sure but
Closes # #25150

Type of change

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

What does this PR do?

My problem was:
When using Model A which had no more limits I wanted opencode to use the Model B as fallback.
This PR fixes the session fallback behavior so Agents can remain on Model A while reliably falling back to Model B when needed. I removed noisy retry status messaging by suppressing repeated rate-limit retry status updates per session after the first occurrence. (Done by config change experimental.suppress_retry_status_message => true)
Furthermore Ipdates the pre-push hook to resolve Bun in our restricted shell environments, preventing turbo package-manager resolution failures during push checks.

If you paste a large clearly AI generated description here your PR may be IGNORED or CLOSED!

How did you verify your code works?

• Ran bun typecheck
• Tested:
  bun test test/session/session.test.ts test/server/session-actions.test.ts
• Built compiled binary with bun run build --single --skip-embed-web-ui
• Verified compiled runtime fallback behavior and output on repeated runs.

Screenshots / recordings

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If this is a UI change, please include a screenshot or recording.

Checklist

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

If you do not follow this template your PR will be automatically rejected.

[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:

Based on my search, I found several related PRs that address similar concerns around retry handling and fallback mechanisms, but no exact duplicates. Here are the most relevant related PRs:

Closely Related (retry/fallback functionality):

• PR fix(session): retry empty stream truncations with attempt cap #26167: fix(session): retry empty stream truncations with attempt cap - Recent session retry improvements
• PR feat(processor): add model fallback chain when retries are exhausted #24369: feat(processor): add model fallback chain when retries are exhausted - Model fallback chain feature
• PR fix(session): retry Codex server_is_overloaded stream errors #25728: fix(session): retry Codex server_is_overloaded stream errors - Session-level retry handling
• PR feat(provider): automatic model fallback on transient errors #20105: feat(provider): automatic model fallback on transient errors - Automatic model fallback

Related (pre-push hook/bun path):

• PR fix: improve scroll behavior and add bun to PATH in hooks #11644: fix: improve scroll behavior and add bun to PATH in hooks - Similar hook path resolution

These PRs address related concerns in the retry and fallback space, but PR #26192 appears to be a distinct implementation combining session fallback behavior with pre-push hook hardening.

[github-actions]

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