refactor(protocol): swap S-expression grammar for strict JSON Schema

Sostituisce la grammatica S-expression con uno schema JSON stretto. La
grammatica S-expression falliva il parsing nel 64% delle generazioni del
modello Qwen3-235B sul run reale; JSON e' nativo per gli LLM moderni e
si parsa con json.loads.

Cambiamenti principali:
- grammar.py: costanti rinominate LOGICAL_OPS / COMPARATOR_OPS /
  CROSSOVER_OPS / ACTION_VALUES / KIND_VALUES.
- parser.py: nuovo AST a dataclass tipizzato (OpNode, IndicatorNode,
  FeatureNode, LiteralNode, Rule, Strategy); parse_strategy ora consuma
  JSON tramite json.loads.
- validator.py: walk dispatchato per tipo (isinstance) invece di
  pattern-matching su 'kind'; arity check su operatori e indicator.
- compiler.py: traversal del nuovo AST tipizzato, dispatch per
  isinstance; logica indicator/feature/literal invariata.
- hypothesis.py: prompt SYSTEM riscritto con esempi JSON e vincoli
  espliciti su no-nesting; estrazione via fence ```json``` + fallback
  brace-balanced.
- __init__.py: re-export pubblico delle entita' del protocollo.
- Tutti i test (parser, validator, compiler, hypothesis_agent,
  falsification, adversarial, e2e, smoke_run) migrati a JSON.
- Rimossa dipendenza sexpdata da pyproject.toml + uv.lock.

Test: 135 passed (era 122; aggiunti casi parser/validator).
ruff + mypy strict clean. Smoke run end-to-end OK.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

uv.lock

@@ -560,7 +560,6 @@ dependencies = [
     { name = "pyyaml" },
     { name = "requests" },
     { name = "scipy" },
-    { name = "sexpdata" },
     { name = "sqlmodel" },
     { name = "streamlit" },
     { name = "tenacity" },
@@ -590,7 +589,6 @@ requires-dist = [
     { name = "pyyaml", specifier = ">=6.0" },
     { name = "requests", specifier = ">=2.32" },
     { name = "scipy", specifier = ">=1.14" },
-    { name = "sexpdata", specifier = ">=1.0.2" },
     { name = "sqlmodel", specifier = ">=0.0.22" },
     { name = "streamlit", specifier = ">=1.40" },
     { name = "tenacity", specifier = ">=9.0" },
@@ -1321,15 +1319,6 @@ wheels = [
     { url = "https://files.pythonhosted.org/packages/07/39/338d9219c4e87f3e708f18857ecd24d22a0c3094752393319553096b98af/scipy-1.17.1-cp314-cp314t-win_arm64.whl", hash = "sha256:200e1050faffacc162be6a486a984a0497866ec54149a01270adc8a59b7c7d21", size = 25489165, upload-time = "2026-02-23T00:22:29.563Z" },
 ]
 
-[[package]]
-name = "sexpdata"
-version = "1.0.2"
-source = { registry = "https://pypi.org/simple" }
-sdist = { url = "https://files.pythonhosted.org/packages/a7/7f/369a478863a39351be75e0a12602bc29196b31f87bf3432bed2be6379f8e/sexpdata-1.0.2.tar.gz", hash = "sha256:92b67b0361f6766f8f9e44b9519cf3fbcfafa755db85bbf893c3e1cf4ddac109", size = 8906, upload-time = "2024-01-09T07:09:59.096Z" }
-wheels = [
-    { url = "https://files.pythonhosted.org/packages/f1/f3/ec9f8cc20dc1f34c926f0ec3f43b73fa2da59cf08e432fb8ae5b666b2027/sexpdata-1.0.2-py3-none-any.whl", hash = "sha256:b39c918f055a85c5c35c1d4f7930aabb176bd29016e5ba5692e7e849914b2a1a", size = 10337, upload-time = "2024-01-09T07:09:57.185Z" },
-]
-
 [[package]]
 name = "six"
 version = "1.17.0"