v0.3.0 — 10.50 tok/s, faster than the C reference on every stage

What's Changed

• measure the memory system; correct three claims; record two dead ends by @Bellman281 in #20
• build: 120 MHz MSPI as an opt-in overlay — 9.75 tok/s, one flag away by @Bellman281 in #21
• perf(head): 10.50 tok/s — i16 activations and two rows per pass by @Bellman281 in #22
• docs: 91.8 ms with --fast-mspi; language bar says Rust by @Bellman281 in #23

Full Changelog: v0.2.0...v0.3.0