Summary

This commit adds full IndexBinaryOp UDT support and a suite of SuiteSparse JIT reliability fixes.

New Features

IndexBinaryOp on User-Defined Types (UDTs)

• IndexBinaryOp._compile_udt now works for UDT operands, including UDT theta values. A new _get_udt_wrapper_indexbinary helper in base.py generates the Numba cfunc wrapper for the 4-index + theta signature (x, ix, jx, y, iy, jy, theta → z).
• _BoundIndexBinaryOp (the result of ibo[dtype](theta)) gained pickling support via __reduce__, proper type markers (_is_udt, commutes_to, etc.), and stores _theta for round-trip serialization.
• ParameterizedIndexBinaryOp pickle/deserialize now round-trips the is_udt flag.

JIT C Code Generation for UDTs (udt_utils.py — new file, ~979 lines)

• Generates C struct typedefs from numpy dtypes (record and array UDTs), enabling SuiteSparse to JIT-compile optimized kernels instead of falling back to Numba cfuncs.
• Handles nested record UDTs, array UDTs, C-reserved name collisions (synthesizes _gbudt_NNN names automatically), and complex-type field restrictions.
• Provides _compile_codegen — a safe exec-based helper with AST pre-validation and linecache registration for readable tracebacks.

JIT Config Auto-Repair (jit_config.py — new file)

• fix_jit_config(): replaces conda-build-baked compiler paths with one from $CONDA_PREFIX/bin/ or sysconfig, strips stale -isysroot / -fdebug-prefix-map flags, and optionally probes the result with a trivial JIT compile.
• _auto_fix_jit_at_import(): called automatically at gb.ss import time to silently repair common mis-configurations without user intervention.
• jit_compiler_is_usable(): lightweight check (file existence only) for use in warnings.

DataType JIT Introspection

• New jit_c_name and jit_c_definition properties expose the C type name and struct typedef that SuiteSparse actually registered — stable across Python-side renames.
• _set_udt_jit_c_definition() sets GxB_JIT_C_NAME + GxB_JIT_C_DEFINITION on the GrB_Type at registration time.

register_new / register_anonymous Ergonomics

• Both now accept a bare @dataclass class or instance as the sole argument, inferring name from the class name.

Fixes & Improvements

UDT Wrapper Refactor (base.py)

• _get_udt_wrapper was a large monolithic function; it's been decomposed into _input_operand, _output_handler, and _compose_wrapper_body, handling record UDTs (tuple-unpack returns), array UDTs, and BOOL-as-INT8 coercion correctly in all combinations.
• _resolve_udt_return_type resolves Numba BaseTuple return types back to the matching record UDT by field arity and type alignment, with actionable UdfParseError messages when the match fails.

Better UDF Error Messages

• UdfParseError docstring updated to document wrapping of TypingError, LoweringError, UnsupportedError.
• _compile_udf_for_udt catches the full NumbaError hierarchy and surfaces the actionable diagnostic line (via _summarize_numba_typing_error) rather than a raw Numba traceback.
• New NoJITWarning warning class emitted once per process when an auto-lifted UDT op falls back to the cfunc path (JIT compiler unusable, jit_c_control off, or UDT not C-representable).

Scalar / UDT Thunk Binding

• TypedBuiltinIndexBinaryOp.__call__ stores theta_value before wrapping in a Scalar, fixing a round-trip issue for UDT thunks where Scalar.from_value couldn't infer the dtype from a raw numpy array.

Tests & Docs

• test_indexbinary.py expanded with UDT cases, pickling, and semiring round-trips.
• test_op.py added ~1,200 lines covering UDT operator compilation, JIT codegen, and error paths.
• test_ssjit.py expanded with JIT auto-fix, NoJITWarning, and C typedef generation tests.
• test_dtype.py and test_pickle.py extended for new jit_c_name/jit_c_definition and register_new(dataclass) behaviour.
• New user guide pages: udt.rst (UDT reference) and updated udf.rst and operators.rst.