refactor(dna): optimize char classification and fix Unicode math symbol misclassification

- Pre-defined and unified character sets (OPERATOR_CHARS, BRACKET_CHARS, PUNCT_CHARS, WHITESPACE_CHARS).
- Defined precise sets for SYMMETRY_CHARS, PERIODICITY_CHARS, CONTINUITY_CHARS, and META_MATH_CHARS.
- Re-ordered specific checks to precede c.isalpha() so Unicode/Greek math letters are not misclassified as standard lower/upper alpha.

Build: 3307 jobs, 0 errors (lake build)

python/phi/charclass.py

@@ -35,7 +35,14 @@ CHAR_CLASSES = {
 
 OPERATOR_CHARS = set("+-*/^%=<>!&|~")
 BRACKET_CHARS = set("()[]{}")
-PUNCT_CHARS = set(".,;:'\"@#$\\")
+PUNCT_CHARS = set(".,;:'\"@#$\\_")
+WHITESPACE_CHARS = set(" \t\n\r")
+
+# Unicode mathematical sets (placed at the top to prevent misclassification as standard alpha)
+SYMMETRY_CHARS = set("≈≡∼")
+PERIODICITY_CHARS = set("πθλ∞")
+CONTINUITY_CHARS = set("→Δ∇∫")
+META_MATH_CHARS = set("√∑∏∂")
 
 
 def classify_char(c: str) -> int:
@@ -84,31 +91,30 @@ def classify_char(c: str) -> int:
         >>> classify_char("©")
         7
     """
+    # Check Unicode math classes first so Greek/math symbols are not misclassified as standard alpha
+    if c in PERIODICITY_CHARS:
+        return 9
+    if c in CONTINUITY_CHARS:
+        return 10
+    if c in SYMMETRY_CHARS:
+        return 8
+    if c in META_MATH_CHARS:
+        return 11
+
+    # Check standard ASCII classes
     if c.isdigit():
         return 0
     if c.isalpha():
         return 1 if c.islower() else 2
-    # Operator chars
-    if c in "+-*/^%=<>!&|~":
+    if c in OPERATOR_CHARS:
         return 3
-    # Bracket chars
-    if c in "()[]{}":
+    if c in BRACKET_CHARS:
         return 4
-    # Punctuation
-    if c in ".,;:'\"@#$\\":
+    if c in PUNCT_CHARS:
         return 5
-    # Whitespace
-    if c in (" ", "\t", "\n", "\r"):
+    if c in WHITESPACE_CHARS:
         return 6
-    # Other (General)
-    if c in "$\\pi\\theta\\lambda\\infty$": # Periodicity
-        return 9
-    if c in "$\\rightarrow\\Delta\\nabla\\int$": # Continuity
-        return 10
-    if c in "=$\\approx\\equiv\\sim$": # Symmetry
-        return 8
-    if c in "$\\sqrt{}\\sum\\prod\\partial$": # Meta-math
-        return 11
+
     return 7