feat: add FLUX.2 Klein model support

Add support for FLUX.2 Klein distilled models (4B and 9B variants):

- Add pipeline loader for Flux2KleinPipeline
- Add model detection for 'flux.2' + 'klein' patterns
- Add pipeline mapping in shared_items
- Add shared Qwen3ForCausalLM text encoder handling:
  - 4B variants use Z-Image-Turbo's Qwen3-8B
  - 9B variants use FLUX.2-klein-9B's Qwen3-14B
- Add reference entries for distilled (4B, 9B) and base models
- Update diffusers commit for Flux2KleinPipeline support

html/reference.json

@@ -124,6 +124,24 @@
     "size": 104.74,
     "date": "2025 November"
   },
+  "Black Forest Labs FLUX.2 Klein Base 4B": {
+    "path": "black-forest-labs/FLUX.2-klein-base-4B",
+    "preview": "black-forest-labs--FLUX.2-klein-base-4B.jpg",
+    "desc": "FLUX.2-klein-base-4B is the undistilled 4 billion parameter base model of FLUX.2-klein. Requires 50 inference steps for full quality but offers flexibility for fine-tuning. Fits in ~13GB VRAM. Supports text-to-image and multi-reference editing. Apache 2.0 licensed.",
+    "skip": true,
+    "extras": "sampler: Default, cfg_scale: 4.0, steps: 50",
+    "size": 8.5,
+    "date": "2025 January"
+  },
+  "Black Forest Labs FLUX.2 Klein Base 9B": {
+    "path": "black-forest-labs/FLUX.2-klein-base-9B",
+    "preview": "black-forest-labs--FLUX.2-klein-base-9B.jpg",
+    "desc": "FLUX.2-klein-base-9B is the undistilled 9 billion parameter base model of FLUX.2-klein. Requires 50 inference steps for full quality but offers flexibility for fine-tuning. Requires ~29GB VRAM. Supports text-to-image and multi-reference editing. Non-commercial license.",
+    "skip": true,
+    "extras": "sampler: Default, cfg_scale: 4.0, steps: 50",
+    "size": 18.5,
+    "date": "2025 January"
+  },
 
   "Z-Image-Turbo": {
     "path": "Tongyi-MAI/Z-Image-Turbo",