Introduce MistralRequestCoordinator and queued auto-screenshot handling

[Android-PowerUser]

Motivation

• Centralize and harden Mistral API request coordination and retry/cooldown logic to replace duplicated ad-hoc implementations.
• Prevent excessive parallel Mistral requests from auto-screenshot flow by serializing and queueing screenshot-triggered calls.

Description

• Add a new coordinator network/MistralRequestCoordinator.kt that encapsulates key cooldowns, adaptive retries, parsing of Retry-After and x-ratelimit-reset headers, and selection of API keys via execute(...) returning MistralCoordinatedResponse.
• Replace custom request/retry/cooldown code in ScreenCaptureApiClients.callMistralApi to use MistralRequestCoordinator.execute(...) when executing HTTP calls.
• Replace the large ad-hoc Mistral retry and key-cooldown loop in PhotoReasoningViewModel.reason(...) with a call to MistralRequestCoordinator.execute(...) and remove redundant key bookkeeping logic.
• Add queuing for auto screenshot-triggered Mistral requests in PhotoReasoningViewModel by introducing QueuedMistralScreenshotRequest, enqueueMistralAutoScreenshotRequest, dispatchMistralAutoScreenshotRequest, and releaseAndDrainMistralAutoScreenshotQueue to ensure only one in-flight Mistral auto-request and latest-wins queuing.
• Wire the queue drain to the existing finally block so queued screenshot requests are drained after each Mistral call completes.

Testing

• Built the app and run unit tests with ./gradlew assembleDebug and ./gradlew test, and the build and unit tests completed successfully.
• Manually exercised the Mistral call paths in debug runs to validate coordinator selection and that auto-screenshot requests are queued and subsequently dispatched (no automated UI tests were added).

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Codex Task

[amazon-q-developer]

Review Summary

The PR successfully introduces MistralRequestCoordinator to centralize Mistral API request coordination with adaptive retry logic and cooldown management. The queuing mechanism for auto-screenshot requests prevents excessive parallel requests. The implementation is clean and well-structured.

Key Changes:

• ✅ New MistralRequestCoordinator encapsulates cooldowns, retry logic, and header parsing
• ✅ Replaced ad-hoc retry logic in both ScreenCaptureApiClients and PhotoReasoningViewModel
• ✅ Added queuing for auto-screenshot-triggered Mistral requests with latest-wins strategy
• ✅ Proper integration with finally blocks for queue draining

The changes are well-implemented and ready for merge. No blocking issues found.

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