fix(mcp-image-gen): rewrite flux2_klein_heretic workflow with CFGGuider + correct node types

- Replace FluxDisableGuidance+BasicGuider chain with CFGGuider (cfg=5)
- CLIPLoader: add device='default', keep type='flux2'
- UNETLoader: weight_dtype='default' (not fp8_e4m3fn — avoids dimension mismatch)
- VAEDecode/SaveImage: updated node IDs (11→VAEDecode, 12→SaveImage)
- Encoder: qwen_3_4b_bfl.safetensors (7.5GB BFL-merged shards)
- Tests: update heretic model assertions for new node structure (37/37 pass)
- Add RECAP doc with root cause analysis and session history

mcp/mcp-image-gen/tests/test_server.py

@@ -63,11 +63,19 @@ def test_build_flux_workflow_heretic_model():
         seed=42,
         model="flux-2-klein-4b.safetensors",
     )
-    assert wf["6"]["class_type"] == "CLIPTextEncode"
-    assert wf["30"]["class_type"] == "CLIPLoader"  # Qwen3-4B uses single CLIPLoader
-    assert wf["32"]["inputs"]["unet_name"] == "flux-2-klein-4b.safetensors"
-    assert wf["31"]["inputs"]["vae_name"] == "flux2-vae.safetensors"
-    assert wf["13"]["inputs"]["scheduler"] == "beta"  # FLUX.2 Klein uses beta scheduler
+    # New FLUX.2 workflow uses different node IDs and types
+    assert wf["1"]["class_type"] == "CLIPLoader"          # Qwen3-4B uses single CLIPLoader
+    assert wf["1"]["inputs"]["type"] == "flux2"            # correct type for FLUX.2
+    assert wf["1"]["inputs"]["device"] == "default"        # required for FLUX.2 CLIPLoader
+    assert wf["2"]["class_type"] == "CLIPTextEncode"       # standard CLIP encode (not Flux-specific)
+    assert wf["4"]["class_type"] == "UNETLoader"
+    assert wf["4"]["inputs"]["unet_name"] == "flux-2-klein-4b.safetensors"
+    assert wf["4"]["inputs"]["weight_dtype"] == "default"  # not fp8 — avoids dimension errors
+    assert wf["6"]["class_type"] == "EmptyFlux2LatentImage"  # FLUX.2-specific latent
+    assert wf["8"]["class_type"] == "CFGGuider"            # CFGGuider replaces FluxDisableGuidance+BasicGuider
+    assert wf["8"]["inputs"]["cfg"] == 5                   # cfg=5 for FLUX.2 Klein
+    assert wf["11"]["class_type"] == "SamplerCustomAdvanced"  # FLUX.2 sampler (node 11, not 12)
+    assert wf["13"]["class_type"] == "SaveImage"           # output node
 
 
 def test_workflow_registry_contains_both_models():