fix: OpenAI Responses system role, background spinner, and shell prompt improvements

[elkaix]

Summary

• Fix OpenAI Responses role=\"system\" sent to newer models. The system→developer conversion was gated on a stale literal list; now runs unconditionally in OpenAIResponses so all local system messages are normalized. Also fixes the _carry_context_to_session path that re-sent a seeded role=\"system\" summary on the first request after a model switch.
• Background bash tasks no longer show the agent verb spinner. Pure-bash background work shows a fixed "Running in background…" label; mixed bash+agent work keeps the verb spinner while the agent is active.
• Quiet background tasks drop to idle repaint rate. After 2 s of no output the refresh loop steps down to 1.0 s instead of spinning braille at 12.5 fps — fixes the "stuck spinner" look for long-running dev servers.
• Welcome banner no longer shows stale "Update available" chip after /update. Mirrors the under-input notice: shows "Updated X → vY. Restart to apply." when the update already landed this session.

Test plan

• make check-pythinker-code && make test-pythinker-code green
• Send a message with a GPT-5.5/gpt-5.3-codex model — confirm no System messages are not allowed error
• Start a long-running background bash task — confirm verb spinner does not appear
• Run /update then open a new session — confirm banner chip shows "Updated" not "Update available"

Summary by CodeRabbit

• Chores
  • Updated changelog formatting.

[coderabbitai]

No actionable comments were generated in the recent review. 🎉

ℹ️ Recent review info

⚙️ Run configuration

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Run ID: fb5ad3b9-122e-4aa4-8c09-f41bfdb49f59

📥 Commits

Reviewing files that changed from the base of the PR and between af9388f and 742a79a.

⛔ Files ignored due to path filters (1)

• tasks/implementer-judge-chain-plan.md is excluded by !tasks/**

📒 Files selected for processing (1)

• CHANGELOG.md

💤 Files with no reviewable changes (1)

• CHANGELOG.md

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📝 Walkthrough

Walkthrough

Removes one blank line in CHANGELOG.md between two consecutive bullet entries in the Unreleased section, normalizing list formatting.

Changes

CHANGELOG Formatting Fix

Layer / File(s)	Summary
Unreleased section bullet spacing CHANGELOG.md	Removes the extra blank line between the "Bundled judge-branded skills" entry and the "Fix OpenAI Responses requests…" entry.

Estimated code review effort

🎯 1 (Trivial) | ⏱️ ~1 minutes

Suggested labels

bug

🚥 Pre-merge checks | ✅ 3 | ❌ 2

❌ Failed checks (2 warnings)

Check name	Status	Explanation	Resolution
Title check	⚠️ Warning	The title follows conventional commits format with 'fix' type but describes multiple unrelated changes (OpenAI, spinner, shell prompt) rather than the actual changeset (CHANGELOG.md formatting).	Align the title with the actual changeset. The PR only modifies CHANGELOG.md formatting, so use: 'docs: Normalize CHANGELOG.md markdown formatting' or similar.
Description check	⚠️ Warning	The description is misaligned with the changeset. It describes multiple features (OpenAI fixes, spinner improvements, update banner) that don't appear in the actual code changes (CHANGELOG.md only).	Ensure the description matches the actual changeset. If these features are in separate commits, split into multiple PRs. If the summary is outdated, update it to reflect only CHANGELOG.md modifications.

✅ Passed checks (3 passed)

Check name	Status	Explanation
Docstring Coverage	✅ Passed	No functions found in the changed files to evaluate docstring coverage. Skipping docstring coverage check.
Linked Issues check	✅ Passed	Check skipped because no linked issues were found for this pull request.
Out of Scope Changes check	✅ Passed	Check skipped because no linked issues were found for this pull request.

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✨ Finishing Touches

🧪 Generate unit tests (beta)

• Create PR with unit tests
• Commit unit tests in branch feat/editor-bug-fixes-draft-autosave

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[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.

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