DOC: note that cpu-baseline=none does not disable CPU dispatch - #32826

PR summary

• Closes DOC: If I build numpy with -Dcpu-baseline="none", will it still generate optimised code paths for newer CPUs? #31073
• The issue asks whether cpu-baseline="none" still builds faster code paths for newer CPUs. The docs didn't say, and an early reply in the thread wrongly said no.
• The answer is yes. Dispatch is separate from the baseline, and with the default cpu-dispatch="max", X86_V2, X86_V3 and newer are still built and picked at runtime. You can check this in meson_cpu/meson.build, where dispatch only skips features already in the baseline. The opt_func_info output posted in the thread shows the same thing.
• On 2026-09-18 a maintainer (InessaPawson) asked for an explicit note saying this. That's what the PR adds, in the "Targeting Older CPUs" section. It also says how to turn dispatch off (cpu-dispatch="none") and points to opt_func_info.
• It also fixes a small typo nearby ("This unsuitable" → "This is unsuitable").

First time contributor introduction

First time contributor here! I'm Nikita at Bloomberg, an engineer on our electronic trading team - previously an ML engineer at DRW and Shopify. Many of my ML and AI initiatives relied on NumPy for core numerical work, which is why I wanted to contribute back.

AI Disclosure

• Tool: Claude Code (Claude Opus 5.5).