cypher-codegen: fix scalar math & numeric arithmetic type inference

[jbmusso]

Summary

Fixes two numeric type-inference gaps in the cypher-codegen type checker (src/frontend/InferType.ts):

1. Scalar math functions were unrecognized. log, log10, exp, sqrt, the trigonometric
   functions, ceil, floor, round, e(), pi(), rand() and friends were absent from the
   function registry and not special-cased, so the checker threw
   CypherTypeError: Unrecognized function '<name>' — a hard codegen failure for any query
   projecting a bare math call (e.g. RETURN log(x) AS weight).
2. Arithmetic typed only the first operand. a * b / a ^ b only inspected the first operand,
   and numeric a + b returned the first operand's type. So Long * Double (or priceLong * 1.5)
   inferred Long, emitting Neo4jInt and risking a runtime decode failure when Neo4j returns a
   float. Compounded by all numeric literals typing as Long (the lexer's DIGIT token doesn't
   distinguish ints from floats).

Changes

• Math functions: added Neo4j scalar math functions to AGGREGATE_RETURN_TYPES — log/log10/
  exp/sqrt/ceil/floor/round/sin/cos/tan/cot/asin/acos/atan/atan2/degrees/
  radians/haversine/e/pi/rand → Double, sign → Long. abs is special-cased to
  preserve its argument's numeric type (abs(Long)=Long, abs(Double)=Double).
• Arithmetic: refactored the addSub/multDiv/power/unary levels of inferExpressionType into
  recursive helpers (inferAddSubType/inferMultDivType/inferPowerType/inferUnaryType) that
  infer every operand and unify them with a numericJoin (Long ⊔ Double = Double). A Double
  anywhere widens the result; ^ yields Double. Non-numeric (date/duration), String-concatenation,
  and list-concatenation cases are preserved.
• Numeric literals: numLit now types literals by their text — 1.5, 1e3, and float-suffixed
  literals infer Double; plain integers infer Long. So priceLong * 1.5 correctly infers
  Double.
• Docs: updated src/frontend/CLAUDE.md (function table + a numeric-arithmetic typing rule).

Tests

Reproduce-then-fix per gap (RED → GREEN → RED → GREEN):

• Added a scalar math functions describe block (log/trig → Double, sign → Long, abs
  input-preserving) — failed with "Unrecognized function" before the fix.
• Added an arithmetic operand typing describe block (Long ⊔ Double = Double, ^ → Double,
  float literals → Double, with String/list concatenation as regression guards) — failed inferring
  Long before the fix.

Full package unit suite passes (215 tests), including CypherCodegen.typecheck which compiles
the generated output under Effect v4 (confirms the Double → Schema.Number codegen path is
unaffected). eslint and tsc are clean.

Note: the Neo4j *.integration.test.ts suite was not run in this environment (Docker
unavailable); changes are confined to type inference and are covered by the unit suite.

A changeset (patch for @evryg/effect-cypher-codegen) is included.