refactor(harness): renaming prodotto tht (Onda -1)

Thoth (tht) è il prodotto, PSD è il cliente. Nessun riferimento al contesto
clinico nel codice.

Rinomine:
- comando+package nsp→tht (dir nsp/→tht/, 46 import, pyproject entry point)
- gate nsp-gate.js→tht-gate.js (+ rewrite token, relayIfNspFails→relayIfThtFails)
- workspace chirone.{example,test}.yaml→tht.{example,test}.yaml (generici)
- env THOTH_→THT_ (19 var) + NSP_ stragglers (NSP_HARNESS_ROOT, NSP_SESSION)
- commenti/docstring chirone/psdwp3/policlinico neutralizzati ('the reference
  implementation', 'the DWH')

Aggiunto [tool.setuptools.packages.find] include=['tht*'] (necessario: l'auto-
discovery rompeva con tht/ + workspaces/ come top-level multipli).

.env operatore aggiornato in-place (prefissi THT_, valori preservati, gitignored).

Verifica: pytest 109 passed, npm test 14 pass, tht phase meta --json OK, zero
residui nsp/THOTH_/NSP_/chirone nel package.

harness/tht/evidence/formula_store.py

@@ -0,0 +1,100 @@
+"""SQL concept->formula evidence store (spec D14b, §4.7).
+
+A concept (e.g. 'fascia pediatrica', 'ablazione') maps to a reusable SQL formula
+(a CASE WHEN ...) that derives it from physical columns. These are reviewable
+units: the gate surfaces a candidate formula, the reviewer approves or rejects it
+(decision types concept_formula_approved / concept_formula_rejected), and approved
+formulas travel with the schema-linking artifact.
+
+Storage: one file per formula, frontmatter YAML + SQL body (same shape as
+EvidenceDoc.parse). Directory layout: <root>/formulas/<slug>-<n>.sql.md.
+Retrieve is by concept (may return several, e.g. competing drafts vs reviewed).
+"""
+from __future__ import annotations
+
+import re
+from pathlib import Path
+from typing import Literal
+
+import yaml
+from pydantic import BaseModel
+
+FORMULAS_SUBDIR = "formulas"
+_SUFFIX_RE = re.compile(r"^(.*?)-(\d+)\.sql\.md$")
+
+
+class ConceptFormula(BaseModel):
+    concept: str
+    columns: list[str] = []
+    sql: str
+    status: Literal["draft", "reviewed"] = "draft"
+    sources: list[str] = []
+
+    @property
+    def _slug(self) -> str:
+        """ASCII slug for the filename (matches textutil.slugify shape)."""
+        import unicodedata
+
+        text = unicodedata.normalize("NFKD", self.concept).encode("ascii", "ignore").decode()
+        return re.sub(r"[^a-z0-9_]+", "-", text.lower()).strip("-") or "formula"
+
+    def dump(self) -> str:
+        meta = self.model_dump(exclude={"sql"}, mode="json")
+        fm = yaml.safe_dump(meta, sort_keys=False, allow_unicode=True)
+        return f"---\n{fm}---\n{self.sql}\n"
+
+    @classmethod
+    def parse(cls, text: str) -> "ConceptFormula":
+        if not text.startswith("---\n"):
+            raise ValueError("frontmatter mancante (atteso '---\\n' iniziale)")
+        try:
+            _, fm, body = text.split("---\n", 2)
+        except ValueError as e:
+            raise ValueError("frontmatter malformato") from e
+        meta = yaml.safe_load(fm)
+        if not isinstance(meta, dict):
+            raise ValueError("frontmatter non valido")
+        return cls.model_validate({**meta, "sql": body.strip("\n")})
+
+
+def _next_path(root: Path, slug: str) -> Path:
+    """First free <slug>-<n>.sql.md path under root (n starts at 1)."""
+    root.mkdir(parents=True, exist_ok=True)
+    existing = sorted(root.glob(f"{slug}-*.sql.md"))
+    n = 0
+    for p in existing:
+        m = _SUFFIX_RE.match(p.name)
+        if m:
+            n = max(n, int(m.group(2)))
+    return root / f"{slug}-{n + 1}.sql.md"
+
+
+def save_formula(root: Path | str, formula: ConceptFormula) -> Path:
+    """Persist a single concept->formula unit under <root>/formulas/. Returns the
+    written path. Append-only: each save writes a new file (so competing drafts and
+    reviewed versions coexist until a curator prunes)."""
+    root = Path(root)
+    formulas_dir = root / FORMULAS_SUBDIR
+    path = _next_path(formulas_dir, formula._slug)
+    path.parent.mkdir(parents=True, exist_ok=True)
+    path.write_text(formula.dump())
+    return path
+
+
+def retrieve_formula(root: Path | str, concept: str) -> list[ConceptFormula]:
+    """All formulas for `concept` under <root>/formulas/. Empty list if none (or if
+    the dir is absent). Multiple results mean competing drafts/versions for the same
+    concept -- the caller (gate) lets the reviewer pick."""
+    root = Path(root)
+    formulas_dir = root / FORMULAS_SUBDIR
+    if not formulas_dir.is_dir():
+        return []
+    out: list[ConceptFormula] = []
+    for f in sorted(formulas_dir.glob("*.sql.md")):
+        try:
+            formula = ConceptFormula.parse(f.read_text())
+        except ValueError:
+            continue  # malformed file: skip, don't crash retrieval
+        if formula.concept == concept:
+            out.append(formula)
+    return out