Docs: TypedPython kernels against JAX (#189)

[b-re-w]

Closes #189

Docs only.

• docs/design/typedpython.md §5.10 (new): positioning (where JAX does not go), the delegation rule (torch only where it performs as well as JAX), and the list of JAX strengths now pending a decision (fusion, autodiff, vmap, transform composition, sharding, TPU/new-GPU maturity, export compatibility).
• §5.2: tile-op CPU reference is pure Python, no numpy; §5.4: IREE as the model-deployment competitor; §5.5: kernel bundles carry IR and emitter versions; §6 step 4: the kernel runs on CPython without JAX, torch or numpy; §8 item 8: the pending list. Taichi moves to §5.11.
• docs/investigations/typedpython-vs-jax.md: the investigation, with the maintainer's two decisions noted at the top.