apl: quicksort.apl runs as-written (+7); Phase 10 complete

Three fixes for Iverson's dfn
{1≥≢⍵:⍵ ⋄ p←⍵⌷⍨?≢⍵ ⋄ (∇⍵⌿⍨⍵<p),(p=⍵)/⍵,∇⍵⌿⍨⍵>p}:

1. parser: standalone op-glyph branch (/ ⌿ \ ⍀) now consumes a
   following ⍨ or ¨ and emits :derived-fn — `⍵⌿⍨⍵<p` parses
   as compress-commute (was previously dropping ⍨)
2. tokenizer: `name←...` (no spaces) now tokenizes as separate
   :name + :assign instead of eating ← into the name. ⎕← still
   stays one token for the output op
3. inline p←⍵⌷⍨?≢⍵ mid-dfn now works via existing :assign-expr

Full suite 585/585. Phase 10 complete (all 7 items ticked).

Remaining gaps for a future phase: heterogeneous-strand inner
product is the only unfinished part — life works after dropping ⊃,
quicksort works directly.

lib/apl/tests/programs-e2e.sx

@@ -128,3 +128,62 @@
           (apl-run "5 5 ⍴ 0 0 0 0 0 0 0 0 0 0 0 1 1 1 0 0 0 0 0 0 0 0 0 0 0")))
       (get (apl-call-dfn-m dfn board) :ravel))
     (list 0 0 0 0 0 0 0 1 0 0 0 0 1 0 0 0 0 1 0 0 0 0 0 0 0)))
+
+(begin
+  (apl-test
+    "quicksort.apl: 11-element with duplicates"
+    (begin
+      (apl-rng-seed! 42)
+      (mkrv
+        (apl-run
+          "quicksort ← {1≥≢⍵:⍵ ⋄ p←⍵⌷⍨?≢⍵ ⋄ (∇⍵⌿⍨⍵<p),(p=⍵)/⍵,∇⍵⌿⍨⍵>p} ⋄ quicksort 3 1 4 1 5 9 2 6 5 3 5")))
+    (list 1 1 2 3 3 4 5 5 5 6 9))
+  (apl-test
+    "quicksort.apl: already sorted"
+    (begin
+      (apl-rng-seed! 42)
+      (mkrv
+        (apl-run
+          "quicksort ← {1≥≢⍵:⍵ ⋄ p←⍵⌷⍨?≢⍵ ⋄ (∇⍵⌿⍨⍵<p),(p=⍵)/⍵,∇⍵⌿⍨⍵>p} ⋄ quicksort 1 2 3 4 5")))
+    (list 1 2 3 4 5))
+  (apl-test
+    "quicksort.apl: reverse sorted"
+    (begin
+      (apl-rng-seed! 42)
+      (mkrv
+        (apl-run
+          "quicksort ← {1≥≢⍵:⍵ ⋄ p←⍵⌷⍨?≢⍵ ⋄ (∇⍵⌿⍨⍵<p),(p=⍵)/⍵,∇⍵⌿⍨⍵>p} ⋄ quicksort 5 4 3 2 1")))
+    (list 1 2 3 4 5))
+  (apl-test
+    "quicksort.apl: all equal"
+    (begin
+      (apl-rng-seed! 42)
+      (mkrv
+        (apl-run
+          "quicksort ← {1≥≢⍵:⍵ ⋄ p←⍵⌷⍨?≢⍵ ⋄ (∇⍵⌿⍨⍵<p),(p=⍵)/⍵,∇⍵⌿⍨⍵>p} ⋄ quicksort 7 7 7 7")))
+    (list 7 7 7 7))
+  (apl-test
+    "quicksort.apl: single element"
+    (begin
+      (apl-rng-seed! 42)
+      (mkrv
+        (apl-run
+          "quicksort ← {1≥≢⍵:⍵ ⋄ p←⍵⌷⍨?≢⍵ ⋄ (∇⍵⌿⍨⍵<p),(p=⍵)/⍵,∇⍵⌿⍨⍵>p} ⋄ quicksort ,42")))
+    (list 42))
+  (apl-test
+    "quicksort.apl: matches grade-up"
+    (begin
+      (apl-rng-seed! 42)
+      (mkrv
+        (apl-run
+          "V ← 8 3 1 9 2 7 5 6 4 ⋄ quicksort ← {1≥≢⍵:⍵ ⋄ p←⍵⌷⍨?≢⍵ ⋄ (∇⍵⌿⍨⍵<p),(p=⍵)/⍵,∇⍵⌿⍨⍵>p} ⋄ quicksort V")))
+    (list 1 2 3 4 5 6 7 8 9))
+  (apl-test
+    "quicksort.apl: source-file as-written runs"
+    (begin
+      (apl-rng-seed! 42)
+      (let
+        ((dfn (apl-run-file "lib/apl/tests/programs/quicksort.apl"))
+          (vec (apl-run "5 2 8 1 9 3 7 4 6")))
+        (get (apl-call-dfn-m dfn vec) :ravel)))
+    (list 1 2 3 4 5 6 7 8 9)))