[Feature] Allow simulation to start from an arbitrary Blender frame

Motivation

The simulation is currently fixed to start at frame 1. For animation work the action often begins much later, sometimes in the thousands, so the solver has to step through a long stretch of essentially idle frames before the part the user cares about begins. This wastes compute time and makes integrating the solver into an existing animation timeline awkward.

Proposal

Add a simulation start-frame setting so the run can begin at an arbitrary Blender frame instead of always frame 1. The captured deformation and the simulated output would be aligned to that start frame, matching the rest of the scene timeline.

Alternatives Considered

• Time-shifting on export: shifting geometry/cache by hand so a frame-1 run lines up with the intended timeline. Workable but manual and error prone, and it does not avoid simulating the idle lead-in.
• Editing the timeline so the action starts at frame 1: disruptive to an established animation setup and not always possible when the scene is shared with other departments.

Additional Context

Raised in a community thread by a user.

Contribution Agreement

• I confirm that any code, patches, scripts, attachments, or other copyrightable material I include in this issue may be used, reproduced, modified, and distributed by this project under the Apache License 2.0 or as otherwise described in CONTRIBUTING.md.
• This is a feature request from the community (please provide a reference below).

Community Reference

https://github.com/st-tech/ppf-contact-solver/discussions/77

Start by locating the Blender integration entry point and the logic that currently fixes simulation startup at frame 1; the issue names no specific file or test. Run the existing simulation workflow to understand its timeline behavior. Done means a user can choose an arbitrary Blender start frame and the captured deformation and simulated output align with that frame.