feat: add ComfyUI-style prompt weighting via compel

- Support (word:weight), [word], ((nested)) syntax
- Support BREAK for conditioning chunking (.and() translation)
- Use CompelForSDXL (modern API, avoids deprecation)
- Add --raw flag to bypass weighting and fall back to plain encoding
- Update README with Prompt Syntax section and examples
- Add docs/comfyui-prompt-style.md with design doc

README.md

@@ -70,6 +70,7 @@ vnasset generate \
 | `--cfg` | `4.5` | CFG scale |
 | `--seed` | `0` | RNG seed (use `random` for random) |
 | `--output` | `output.png` | Output path |
+| `--raw` | `false` | Disable Compel prompt weighting (fall back to plain diffusers encoding) |
 
 When `--seed` is `random`, a random seed is generated and recorded in the
 metadata file.
@@ -154,18 +155,39 @@ implementation that avoids the SDPA dispatch entirely.
 Tested with `torch 2.11.0+rocm7.2`. Newer ROCm nightlies (2.13+, 2.14+) may
 cause GPU crashes. If you encounter segfaults, try matching this version.
 
-## Prompt Compatibility
+## Prompt Syntax
 
-VNAsset uses standard diffusers SDXL encoding, which is equivalent to ComfyUI's
-`BNK_CLIPTextEncodeAdvanced` with `token_normalization=none` and
-`weight_interpretation=comfy` for plain comma-separated prompts.
+VNAsset supports **ComfyUI-style prompt weighting** via the `compel` library.
 
-ComfyUI-specific syntax is **not currently supported**:
-- `(word:1.2)` — prompt weighting
-- `BREAK` — conditioning chunking
+### Weighting
 
-If your prompts rely on these, you'll get different output than the ComfyUI
-workflow. compel integration is planned for later.
+| Syntax | Effect |
+|--------|--------|
+| `(word)` | Boost ×1.1 |
+| `(word:1.5)` | Boost ×1.5 |
+| `(word:0.6)` | De-emphasize ×0.6 |
+| `[word]` | De-emphasize ×0.9 (shorthand) |
+| `\(word\)` | Literal parentheses (escaped) |
+
+```bash
+vnasset generate \
+  --checkpoint models/novaAnimeXL_ilV190.safetensors \
+  --prompt "(masterpiece:1.2), 1girl, (red hair:1.3), blue eyes, [glasses]" \
+  --negative-prompt "(bad quality, worst quality:1.4)" \
+  --steps 20 --seed 42
+```
+
+### BREAK (condition chunking)
+
+Split the prompt into independent conditioning chunks with `BREAK`:
+
+```bash
+vnasset generate \
+  --prompt "1girl, red hair, standing BREAK blue sky, cherry blossoms" \
+  --steps 20 --seed 42
+```
+
+Use `--raw` to bypass weighting and fall back to plain diffusers encoding.
 
 ## Future Improvements
 
@@ -180,5 +202,4 @@ workflow. compel integration is planned for later.
   availability or a ComfyUI installation.
 - **Qwen Image Edit support** — `vnasset edit` and `vnasset pipeline` for
   batch expression/outfit variant editing.
-- **compel prompt weighting** — support `(word:weight)` and `BREAK` syntax for
-  parity with ComfyUI prompt encoding.
+