docs (en, pl) and editors: masks, tails, shuffles, lookup, dot_add, @cpu, cpu_has, Nix

- technicians' guides: section 31 rewritten around kernels (masks, the end of a list, moving lanes,
  int8 dot products, choosing instructions at build and at run time)
- cheat sheets and engineers' guides: the new operations and their IR; how features are found
- Kate and VS Code: @cpu, boolxN and the new built-ins highlighted

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01Psc42moPLwP43Cmb9oZqSR

docs/en/cheatsheet.md

@@ -255,13 +255,19 @@ Types: `f32x4/8/16`, `f64x2/4/8`, `i8x16/32/64`, `i16x8/16/32`, `i32x4/8/16`, `i
 | `f32x8(v)` | an 8-lane vector converted lane by lane (`f32x8(ints)`, `i32x8(floats)`) |
 | `v + w`, `v * 2.0`, `-v` | lane by lane; a plain number counts for every lane (`/` only on floats) |
 | `& \| ^ << >> ~` | lane by lane, whole-number lanes |
-| `v == w`, `v != w` | bool: every lane equal / not |
+| `v < w`, `v == w`, … | a mask `boolx8`: `m.all()`, `m.any()`, `m.count()`, `m & n`, `!m`, `m[i]` |
+| `select(m, a, b)` | lane by lane: `a` where `m` is true, else `b` |
 | `v[i]`, `v[i] = x`, `v.len` | a lane; the number of lanes |
 | `min(v, w)`, `max`, `abs(v)`, `clamp(v, lo, hi)` | lane by lane |
 | `v.sum()`, `v.min()`, `v.max()`, `v.dot(w)` | one number from all the lanes |
 | `v.sqrt()`, `v.floor()`, `v.ceil()`, `v.round()` | every lane (float lanes) |
 | `v.fma(b, c)`, `v.muladd(b, c)` | `v * b + c`: one rounding always / the fastest way here |
 | `v.store(list, i)` | lanes into `list[i]` … |
+| `f32x8(list, i, fill)`, `v.store_part(list, i)` | the end of a list: only the lanes inside it (the others are `fill`) |
+| `v.shuffle(3, 2, 1, 0)`, `v.lo()`, `v.hi()`, `concat(a, b)` | lanes rearranged (shuffle takes numbers written in the code) |
+| `table.lookup(idx)` | `table[idx % table.len]` per lane (`pshufb`, `tbl`) |
+| `acc.dot_add(a, b)` | `i32x8` sums gain 4 byte products each (`u8x32` × `i8x32`): `vpdpbusd`, `usdot` where there |
+| `@cpu("avx2,fma") fn …`, `cpu_has("avx2")` | a function that may use these features; check at run time before calling it |
 
 ---