[BugFix] reschedule_preempt_task append waiting & PREEMPTED blocksize

[ST-XX]

Motivation

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Modifications

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Checklist

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[paddle-bot]

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Codecov Report

❌ Patch coverage is 0% with 4 lines in your changes missing coverage. Please review.
⚠️ Please upload report for BASE (develop@4eb5533). Learn more about missing BASE report.

Files with missing lines	Patch %	Lines
fastdeploy/engine/sched/resource_manager_v1.py	0.00%	4 Missing ⚠️

Additional details and impacted files

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[Copilot]

Pull request overview

This PR fixes a bug in the request rescheduling logic where preempted requests could be repeatedly rescheduled due to under-allocation of blocks. The fix tracks the block size at preemption time and ensures that rescheduled requests receive at least as many blocks as they had before preemption.

Key Changes:

• Records last_preempted_blocksize when a request is preempted to remember the previous block allocation
• Adds logic to ensure rescheduled requests receive at least the same number of blocks as before to prevent repeated preemption cycles

[Copilot]

The PR description lacks essential information about the motivation and the specific problem being solved. While there is an image reference in the description, there is no text explanation of:

1. What bug is being fixed
2. Why these modifications are necessary
3. What problem scenario triggers the repeated rescheduling issue

Please provide a detailed description explaining the bug scenario, reproduction steps, and how these changes resolve the issue.