feat(chunks): rilevamento universale has_math/has_table + dollarmath plugin

- parser.py: integra dollarmath_plugin (graceful fallback) — blocchi $$…$$ → token math_block atomico
- segmenter.py: gestisce math_block → Block(kind=math, atomic=True, plain_text=[formula])
- packer.py: has_table rileva anche <table> in blocchi html; has_math rileva $$ e \begin{ nel contenuto
- +11 test (parser×3, segmenter×3, packer×5) — totale 65 test

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

chunks/packer.py

@@ -41,9 +41,18 @@ def _build_chunk(blocks: list[Block], index: int, config: ChunkerConfig,
         header_path=header_path,
         block_ids=[b.id for b in blocks],
         flags={
-            "has_code":    any(b.kind == "code"  for b in blocks),
-            "has_table":   any(b.kind == "table" for b in blocks),
-            "has_math":    any(b.kind == "math"  for b in blocks),
+            "has_code":    any(b.kind == "code" for b in blocks),
+            "has_table":   any(
+                b.kind == "table"
+                or (b.kind == "html" and "<table" in b.content.lower())
+                for b in blocks
+            ),
+            "has_math":    any(
+                b.kind == "math"
+                or "$$" in b.content
+                or r"\begin{" in b.content
+                for b in blocks
+            ),
             "is_overflow": total_chars > config.max_chars,
             "is_sparse":   total_chars < config.min_chars,
         },

chunks/parser.py

@@ -2,6 +2,12 @@ from __future__ import annotations
 from markdown_it import MarkdownIt
 from markdown_it.token import Token
 
+try:
+    from mdit_py_plugins.dollarmath import dollarmath_plugin as _dollarmath
+    _HAS_DOLLARMATH = True
+except ImportError:
+    _HAS_DOLLARMATH = False
+
 
 def parse(source: str) -> tuple[list[Token], list[str]]:
     """Parsa Markdown in token stream con source map.
@@ -11,6 +17,8 @@ def parse(source: str) -> tuple[list[Token], list[str]]:
         lines:  righe sorgente (0-indexed) per ricostruzione testo esatto
     """
     md = MarkdownIt().enable("table")
+    if _HAS_DOLLARMATH:
+        md = md.use(_dollarmath, allow_labels=False, allow_space=False)
     tokens = md.parse(source)
     lines = source.splitlines()
     return tokens, lines

chunks/segmenter.py

@@ -191,6 +191,25 @@ def segment(tokens: list[Token], lines: list[str], config: ChunkerConfig) -> lis
             i += 1
             continue
 
+        # ── Math block (dollarmath plugin) ───────────────────────────────────
+        if tok.type == "math_block":
+            start = tok.map[0] if tok.map else 0
+            end = tok.map[1] if tok.map else start + 1
+            content = _lines_content(lines, start, end)
+            blocks.append(Block(
+                id=_make_id(),
+                kind="math",
+                content=content,
+                plain_text="[formula]",
+                atomic=True,
+                start_line=start,
+                end_line=end,
+                header_path=header_path,
+                chars=len(content),
+            ))
+            i += 1
+            continue
+
         # ── HTML block ────────────────────────────────────────────────────────
         if tok.type == "html_block":
             start = tok.map[0] if tok.map else 0