v1.2.6 - Flux 2 & Minimax H3 API

FLUX.2 & MiniMax H3

Four commits on top of main. Adds FLUX.2 to the local engine, the MiniMax H3
family as API nodes, and getting-started cards so a new project is one click from
a working graph.

FLUX.2 (local)

One node covers the whole family. Pick a checkpoint in the Adjust sidebar and it
identifies itself: klein 4B, klein 9B, either Base build, the KV variant, or dev.
Steps and guidance default to "from model", so swapping a distilled checkpoint for
its Base build moves 4 steps at guidance 1.0 to 50 at guidance 4.0 with no settings
to touch.

• Identified by content, never by filename. diffusion_models/ is shared
  across architectures, so checkpoints are read from their tensor shapes. Z-Image,
  Krea 2 and FLUX.2 sit side by side safely.
• Diffusers folders count as checkpoints. That is the only practical way to
  get the 32B dev build onto a 24 GB card, since NF4 shards stream through
  from_pretrained where from_single_file cannot quantize at all.
• Multi reference composition. Wire several images into one node and address
  them by position: "the character from image 1 wearing the jacket from image 2".
  The node numbers them on its face. No denoise strength slider, because FLUX.2
  has no img2img, a single reference is the edit.
• ControlNet, and LoRA training in the Trainer tab against Base builds.
  The trainer refuses a distilled checkpoint rather than letting a run produce a
  bad adapter hours later.
• Staged loading when the encoder and transformer cannot be co-resident. The
  prompt is encoded first and the encoder freed before the transformer loads.

MiniMax H3 (API nodes)

Three nodes: text to video, image to video, reference to video. 2K, 5 to 15
seconds, $0.26 per second, with a live estimate on the node.

• Image to video has two image ports. Wire a start frame alone, or add an end
  frame and H3 interpolates between them.
• Reference to video takes up to 9 images plus reference video and audio. The
  prompt addresses them by position, and wiring order is the numbering you see.
  Over-wired sets trim to fal's caps instead of failing at the API.
• No seed and no prompt optimizer. Neither exists in H3's schema, unlike the older
  MiniMax endpoints.

Getting-started cards

An empty canvas now offers five ways to start. Each card says how that model will
run on your specific GPU, and one click builds a prompt node wired into a model
node with settings and a prompt already filled in. Includes an API Nodes card for
anyone with no GPU.

Advice is advisory, never gating. The device policy quantizes and offloads to fit,
so every tier still says it runs.

Per-port input routing

Inputs now record which port they were wired to, so a model can declare two ports
of the same kind and tell them apart. That is what makes the end frame work.

Untagged inputs still resolve by media kind, so existing projects and drag-and-drop
behave exactly as before.

Fixes

• Wiring a Load Assets node into a Generate node drew an edge and recorded nothing.
  The request went out with an empty URL, and fal answered with a 422 that pointed
  nowhere near the cause.
• A FLUX.2 model pick stored as a full path resolved to nothing and surfaced as
  'None' is not a FLUX.2 diffusion model.
• FLUX.2's pre-flight check reported a checkpoint present when only the variant
  param resolved, so a missing file failed late and opaquely instead of at the
  guard.
• Number params in the fal Adjust panel could not be cleared. An emptied box
  snapped straight back to 0, and an out-of-range value stuck in the field while
  the request quietly used a different one.
• Prompt nodes showed empty text when something wrote the prompt just after mount.
• 21 engine tests were silently not running. They do now.

Upgrading

Projects gain a nullable handle column on first open (SCHEMA_VERSION 16 to 17).
Additive, so older builds still open projects touched by this one.

Pin the version when installing. PyPI sorts 1.2.6 below 1.2.53, so a plain
pip install still resolves to the previous release:

pip install inline-core==1.2.6 inline-studio-frontend==1.2.6

Full Changelog: v1.2.53...v1.2.6