generate_config/compile_kernel/load_module also recorded the last build
directory and PTX in ContextVars so that bare compile_kernel() and
load_module() calls worked: a second, implicit interface beside the
explicit build_dir/ptx_path one used by every owner. compile_kernel now
requires build_dir= and load_module requires the PTX path.
Build contract tests use explicit paths; they still check per-build
header/output isolation, interleaved generation, path escapes, refusal of a
removed snapshot, and that a failed compile keeps the previous PTX and
leaves no partial output. No kernel, numerical or launch change.
Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
