TypedPython: parallel order-independent loops after free-threaded support #151

Approved by the user (2026-10-04), after free-threaded CPython support (AGENTS.md section 12.8, ROADMAP section 9). Parallelise only loops whose result does not depend on iteration order (element-wise writes to distinct indices, no shared reductions), or reductions evaluated in a fixed order, so results stay bit-identical to CPython. Depends on Py_mod_gil declaration safety (pypackpack #60 note) and on #141 phase 2.

Done when: a design note and SPEC item exist; implementation is planned separately.