feat(sterni/aoc/2022): day05 BQN solution

First input that is genuinely fun to parse in BQN. There surely is a
nice trick for _ApplyCmd, but this works and I'm unable to think today.

Change-Id: Iefccc81f1c1db03f45e31aaf7a1703ac0f91306f
Reviewed-on: https://cl.tvl.fyi/c/depot/+/7529
Autosubmit: sterni <sternenseemann@systemli.org>
Reviewed-by: sterni <sternenseemann@systemli.org>
Tested-by: BuildkiteCI

users/sterni/exercises/aoc/2022/05/5.bqn

@@ -0,0 +1,20 @@
+⟨ReadDec, SplitOn, IsAsciiNum⟩ ← •Import "../../lib.bqn"
+rs‿rc ← (<"") SplitOn •FLines "../05/input"
+
+stacks ← {
+  count ← '0'-˜⊑⌽' ' (≠/⊢) ⊑⌽rs
+  spec ← 0<(-1)↓(-1)⌽∾(∾⟜0‿0‿0)¨1+↕count
+  ' ' (≠/⊢)¨⥊⋈˘⍉>spec⊸/¨(-1)↓rs
+}
+
+cmds ← {0‿1‿1-˜ ReadDec¨ ((∧´IsAsciiNum)¨/⊢) (<' ') SplitOn 𝕩}¨ rc
+
+ModestTake ← ↑⍟(<⟜≠)
+_ApplyCmd ← {
+  c‿f‿t ← 𝕩
+  m ← 𝔽 c ModestTake f⊑𝕨
+  (m⊸∾)⌾(t⊸⊑) (c⊸↓)⌾(f⊸⊑)𝕨
+}
+
+•Out "day05.1: "∾⊑¨stacks ⌽_ApplyCmd˜´ ⌽ cmds
+•Out "day05.2: "∾⊑¨stacks ⊢_ApplyCmd˜´ ⌽ cmds