fix: Complete generation queue retry coverage for LEGO, cover, repaint, and vocal workflows

[ChuxiJ]

Problem

Generation queue retry is incomplete across several AI workflows. Failed LEGO/Add Layer/MultiTrack/Cover/Repaint/Vocal jobs can lack retryParams, so the Retry action may be missing or unable to reconstruct the original job.

Root Cause

Queue retry support was added around common generation paths, but job-specific parameter capture was not normalized across all pipeline entry points.

Solution

• Define a shared retry payload contract for every generation job type.
• Capture retry params for LEGO, Add Layer, MultiTrack, Cover, Repaint, and Vocal workflows.
• Add tests for failed job -> visible Retry -> successful replay for each job type.

Verification

• Add unit tests around generationPipeline job creation and retry payloads.
• Add UI/component test for queue retry visibility per job type.
• Run focused AI generation queue tests.

Files to Touch

• src/services/generationPipeline.ts
• src/store/generationStore.ts
• src/components/generation/*
• src/services/__tests__/*generation*