feat(evidence): build semantic fragments from typed units

harness/tht/evidence/canonical.py

@@ -20,7 +20,7 @@ class StrictModel(BaseModel):
     model_config = ConfigDict(extra="forbid")
 
 
-EvidenceKind = Literal[
+EVIDENCE_KINDS = (
     "glossary",
     "domain",
     "enum",
@@ -29,13 +29,15 @@ EvidenceKind = Literal[
     "normalization",
     "formula",
     "reference",
-]
-EvidencePurpose = Literal[
+)
+EVIDENCE_PURPOSES = (
     "disambiguation",
     "rewriting",
     "schema_linking",
     "sql_generation",
-]
+)
+EvidenceKind = Literal[*EVIDENCE_KINDS]
+EvidencePurpose = Literal[*EVIDENCE_PURPOSES]
 _IDENTIFIER = r"[A-Za-z_][A-Za-z0-9_$]*"
 _TABLE_IDENTIFIER = re.compile(rf"^{_IDENTIFIER}\.{_IDENTIFIER}$")
 _COLUMN_IDENTIFIER = re.compile(rf"^{_IDENTIFIER}\.{_IDENTIFIER}\.{_IDENTIFIER}$")