fix: resolve Gemini history image references

[SunmiJJW]

Gemini conversation history can contain image references accepted by AstrBot's shared media resolver, including local paths. The adapter's history converter still assumed every image was a base64 data URI, so a local history image raised before the provider request and triggered fallback.

Modifications / 改动点

• Resolve Gemini history image references through the existing shared media resolver.

• Make conversation preparation asynchronous and await it in both streaming and non-streaming request paths.

• Add a regression test for a local WebP history image and update existing conversation tests for the async preparation path.

• No new dependencies.

• This is NOT a breaking change. / 这不是一个破坏性变更。

Verification steps / 验证步骤

1. Run: python -m pytest -q tests/test_gemini_source.py
2. Run Ruff check and format check for the two changed files.
3. Compile gemini_source.py.

Test results / 运行结果

• Gemini provider tests: 7 passed.
• Ruff check: passed.
• Ruff format check: passed.
• Compile check: passed.

Checklist / 检查清单

• This is a bug fix, not a new feature.
• My changes have been well-tested, and verification steps/results are provided above.
• No new dependencies are introduced.
• My changes do not introduce malicious code.

Summary by Sourcery

Fix Gemini history image handling so supported media references are resolved before provider requests.

Bug Fixes:

• Resolve image references in Gemini conversation history through the shared media resolver, including local image paths, instead of assuming base64 data URIs.

Enhancements:

• Make Gemini conversation preparation asynchronous and await it for both streaming and non-streaming requests.

Tests:

• Add regression coverage for resolving a local WebP history image and update conversation preparation tests for asynchronous execution.

[chatgpt-codex-connector]

Codex Review Summary

This comment shows the latest Codex review activity on this pull request.

Review	Status	Commit	Review trigger
📝 Code Review	✅ Completed 2026-08-30T07:46:15.005294Z	88768d0	PR opened

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[sourcery-ai]

Hey - I've reviewed your changes and they look great!

Sourcery assessment

Approved.

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