refactor(types): shrink src/types.zig to editor/parse metadata (A8.2)

Remove the legacy parallel type model's compiler-like surface. The
compiler pipeline resolves/lowers/lays out against canonical
src/ir/types.zig (TypeId/TypeTable); src/types.zig.Type is now strictly
editor-indexing + parse-time name metadata.

- src/types.zig: delete the type-resolution surface (widen, bitWidth,
  isImplicitlyConvertibleTo) and every helper left dead once it was gone
  (eql, isInt/isFloat/isSigned/isUnsigned, isTuple/isVector, and the
  already-unused classification predicates isEnum/isUnion/isString/
  isStringLike/isAny/optionalChild/sliceElementType/manyPointerElementType/
  vectorElementType/isFunctionType/isClosureType/isCallable). Keep the Type
  union plus the display/name-classification helpers sema/lsp/parser use
  (fromName, fromTypeExpr, toName, displayName, isStruct/isOptional/isSlice/
  isPointer/isManyPointer/isArray, pointerPointeeType). Seal the file with a
  doc comment.
- src/sema.zig: inferExprType no longer calls Type.widen for arithmetic;
  it approximates the display type as the left operand's (no second
  resolver in the editor index).
- src/ir/type_bridge.zig: delete the dead bridgeType (legacy Type -> TypeId)
  function + its sole sx_types import; resolveAstType and the AST->TypeId
  path are untouched.
- src/ir/ir.zig: drop the bridgeType re-export.
- src/ir/type_bridge.test.zig: drop the two bridgeType tests (function gone).

Gate: zig build, zig build test (exit 0), tests/run_examples.sh 361/0,
zero examples/expected churn.

src/ir/ir.zig

@@ -64,7 +64,6 @@ pub const LLVMEmitter = emit_llvm.LLVMEmitter;
 
 pub const type_bridge = @import("type_bridge.zig");
 pub const resolveAstType = type_bridge.resolveAstType;
-pub const bridgeType = type_bridge.bridgeType;
 
 pub const jni_descriptor = @import("jni_descriptor.zig");
 pub const jni_java_emit = @import("jni_java_emit.zig");