feat comfyui connector and fix framesync null guard

[ischencheng]

Summary

Introduces a ComfyUI-to-BMF connector that runs ComfyUI graphs on the BMF engine without bundling GPL3.0 code.
Fixes a crash in FrameSync input manager when inputs arrive at different timestamps (mixed-rate/mixed-type flows).

Part 1 — Feature: ComfyUI Connector

What

Runtime integration that converts a ComfyUI prompt graph into a BMF GraphConfig and executes it in-process.

How

• demo/comfyui_intergration/bmf_runner.py: Installs a lightweight runtime hook into execution.PromptExecutor.execute (no on-disk modification) and routes execution into BMF when enabled.
• demo/comfyui_intergration/bridge.py:
  • BmfWorkflowConverter builds a BMF graph from the ComfyUI prompt.
  • ComfyNodeRunner wraps each Comfy node as a BMF module with:
    • zero-copy tensor paths (hmp <-> torch via DLPack),
    • simple model-output caching for loader nodes,
    • progress/preview alignment with comfy_execution.progress,
    • guarded input decoding to avoid null/invalid packets.
• demo/comfyui_intergration/run_bmf_comfy.py: Launches ComfyUI with the runtime hook installed.
• demo/comfyui_intergration/setup.sh: One-step environment setup and pinned ComfyUI checkout.

Why

• Avoid copying GPL-licensed code; only use public modules at runtime.
• Keep ComfyUI UX: progress bars, previews, and history outputs remain aligned.
• Zero-copy data flow reduces CPU/GPU overhead.

Part 2 — Bugfix: FrameSync crash under mixed timestamps

• FrameSync scans inputs, records the next packet per stream (if any), computes the global minimum timestamp min_ts, and only “advances” streams whose next packet timestamp equals min_ts.
• For streams whose next packet is greater than min_ts, curr_pkt_ remains unset. Previously, the code unconditionally called set_timestamp() on curr_pkt_[stream_id]. Because operator[] default-constructs an empty Packet, this dereferenced an invalid packet and crashed.

Fix in this MR:

• Add a defensive null-guard before set_timestamp() and only enqueue defined packets for each stream. This prevents creating invalid packets and eliminates the segfault.
• On the Comfy side, the node runner checks that all input queues are non-empty before executing. If any input is missing, it simply waits, so mixed-rate/mixed-type graphs (e.g., KSampler receiving model/vae at ts=1 and latent at ts=2) no longer crash.

Limitations & follow-ups:

• Some Comfy nodes truly require a strict “all inputs present” barrier at the min_ts step.
• If this fix would change FrameSync semantics in an unacceptable way, consider adding a new input manager (e.g., “AlignedFrameSync”).
• DefaultInputManager/ImmediateInputStreamManager intentionally do not provide this barrier behavior.

Reproducer (why it used to crash)

• Graph with KSampler(e.g. image2image template in ComfyUI):
  • model/vae from a loader arrive once at ts=1.
  • latent_image arrives later at ts=2 (after VAEEncode finishes).
• FrameSync selected min_ts=1, advanced model/vae streams, left latent_image unset.
• Code then attempted set_timestamp() on a default-constructed Packet for latent_image, causing a null dereference.
• The guard added in this MR prevents that; the runner waits until latent_image arrives before executing the node.

[hulibruce]

Good Job! Thanks for the contribution.

[hulibruce]

@ischencheng cloud you please rebase the latest code in master branch? It might fix the CI issue we encountered.

[ischencheng]

@hulibruce Sure—I rebased, and the CI issue is fixed.