Introduce MistralRequestCoordinator and queueing for Mistral auto-screenshots

[Android-PowerUser]

Motivation

• Centralize and simplify Mistral API rate-limiting and retry behavior across the app into a single coordinator to avoid duplicated, error-prone logic.
• Prevent overlapping Mistral streaming requests and ensure a single in-flight auto-screenshot request with a latest-wins queue to reduce wasted calls and respect provider limits.
• Replace ad-hoc per-key cooldown tracking sprinkled through the code with a reusable component.

Description

• Add a new MistralRequestCoordinator (app/src/main/kotlin/com/google/ai/sample/network/MistralRequestCoordinator.kt) that implements cooldown tracking, Retry-After/x-ratelimit-reset parsing, adaptive backoff, and coordinated selection/rotation of API keys via execute(apiKeys, maxAttempts, request).
• Update ScreenCaptureApiClients.callMistralApi to use MistralRequestCoordinator.execute for performing the HTTP call and key rotation instead of calling the endpoint directly.
• Refactor PhotoReasoningViewModel to use the coordinator for reasonWithMistral streaming calls and remove the previous inline per-key cooldown and retry loop.
• Implement a latest-wins queue for automatic screenshot-based Mistral requests: introduce QueuedMistralScreenshotRequest, enqueueMistralAutoScreenshotRequest, dispatchMistralAutoScreenshotRequest, and releaseAndDrainMistralAutoScreenshotQueue to ensure only one in-flight Mistral auto-screenshot request and drain a single queued request afterwards.
• Remove legacy fields and functions related to the old per-key cooldown state and update imports to include MistralRequestCoordinator.

Testing

• Built the app module with ./gradlew :app:assembleDebug and verified the build completes successfully.
• Ran unit tests with ./gradlew :app:test and observed they complete without failures.
• Performed runtime verification of Mistral request flow locally to ensure streaming paths invoke the coordinator and that the auto-screenshot queue dispatches and drains (manual integration check succeeded).

---

Codex Task

[amazon-q-developer]

Summary

This PR introduces MistralRequestCoordinator to centralize rate-limiting logic and implements a screenshot queueing mechanism for Mistral requests. The coordinator provides sophisticated retry logic with cooldown tracking and adaptive backoff.

Critical Issues Found

I've identified 2 critical defects that should be addressed before merging:

1. ScreenCaptureApiClients.kt: The coordinator is invoked with only a single API key, defeating its purpose of multi-key rotation
2. MistralRequestCoordinator.kt: Potential crash from using apiKeys.first() instead of keyPool.first()

Architecture Notes

The refactoring successfully consolidates rate-limiting logic and removes ~130 lines of duplicate code from PhotoReasoningViewModel. The new queueing mechanism for auto-screenshots (latest-wins pattern) is well-designed for preventing overlapping requests.

---

You can now have the agent implement changes and create commits directly on your pull request's source branch. Simply comment with /q followed by your request in natural language to ask the agent to make changes.

[amazon-q-developer]

🛑 Logic Error: Passing only a single API key defeats the purpose of using MistralRequestCoordinator. The coordinator is designed to handle multiple API keys for rotation and fallback, but this implementation provides a list containing only the single apiKey parameter. This means no key rotation will occur even if the coordinator supports it, and the coordinator's multi-key logic becomes redundant overhead.

Either pass all available API keys from ApiKeyManager, or call the Mistral API directly without the coordinator if only one key is intended.

[Android-PowerUser]

/q Fix ScreenCaptureApiClients.kt: The coordinator is invoked with only a single API key, defeating its purpose of multi-key rotation

[amazon-q-developer]

I'll fix the issue where the MistralRequestCoordinator is being invoked with only a single API key, defeating its purpose of multi-key rotation.

Changes I will implement:
• ScreenCaptureApiClients.kt:74-133: Update callMistralApi function signature to accept apiKeys: List<String> instead of apiKey: String and pass all keys to the coordinator for proper rotation
• ScreenCaptureService.kt:299-302: Retrieve all available Mistral API keys from ApiKeyManager and pass them to callMistralApi instead of just the single key from the intent

[amazon-q-developer]

✅ Changes committed successfully!

I've fixed the multi-key rotation issue for the Mistral API coordinator:

Summary of changes:

1. ScreenCaptureApiClients.kt: Updated callMistralApi function to accept apiKeys: List<String> instead of a single apiKey, and now passes all available keys to MistralRequestCoordinator.execute() for proper rotation
2. ScreenCaptureService.kt: Modified the Mistral API call path to retrieve all available Mistral API keys from ApiKeyManager and pass them to callMistralApi

The coordinator can now properly rotate through multiple API keys as originally intended, improving rate limit handling and request reliability.