fix(llm): catch bare "cannot generate" phrasing without a leading "I"

The lexical refusal pattern required an "I" before cannot/can't/won't
so a refusal fragment like "Cannot generate this image due to the
content" (no leading pronoun — the shape it takes as a JSON string
value or a mid-sentence fragment) went undetected. Made the "I"
prefix optional; the cannot/can't/won't-plus-nearby-generate/create/
etc. shape is specific enough that dropping the pronoun requirement
doesn't pick up ordinary content (verified against the existing
"ordinary content" regression cases).

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>

src/comfydv/_llm/retry.py

@@ -60,7 +60,7 @@ def next_seed(options: dict | None, attempt: int) -> int:
 REFUSAL_LEXICAL_PATTERNS: tuple[re.Pattern, ...] = tuple(
     re.compile(p, re.IGNORECASE)
     for p in (
-        r"\bI\s*(?:'m|\s+am)?\s*(?:cannot|can't|won't|will not)\b[^.]{0,60}?\b"
+        r"\b(?:I\s*(?:'m|\s+am)?\s*)?(?:cannot|can't|won't|will not)\b[^.]{0,60}?\b"
         r"(?:generate|create|produce|write|provide|help|assist|describe|depict|continue)\b",
         r"\bI(?:'m|\s+am) (?:not able|unable) to\b",
         r"\bI don't feel comfortable\b",

tests/test_llm_retry.py

@@ -51,6 +51,8 @@ class TestLexicalDetection:
             "I cannot generate that image for you.",
             "I'm not able to help with this request.",
             "I am unable to comply with your instruction.",
+            "Cannot generate this image due to the sensitive content.",
+            '{"error": "cannot generate this content"}',
             "I don't feel comfortable creating this content.",
             "I'm sorry, but I can't produce that description.",
             "As an AI, I'm unable to depict this scenario.",