fix: reset request state and align inference workflows

[zhangbilang]

Fix state reuse across inference requests and consolidate media handling.

• Reset ErnieImage, LongCatImage and ZImage generators for each request.
• Release MiniMax/SeedVR conditioning state and clear NeoPP KV references after execution, including encoder/main failures.
• Preserve Disagg seed precedence with a fallback of 42, seed before model loading, and reseed each execution stage per request.
• Reuse file and media handling, prevent downloads with identical filenames from overwriting inputs, and remove redundant service wrappers.
• Move WorldPlay action checkpoint paths into JSON and propagate invalid pose errors.
• Make Wan example paths and request parameters explicit.