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/parser.sx

@@ -416,10 +416,20 @@
                 ((apl-parse-op-glyph? tv)
                   (if
                     (or (= tv "/") (= tv "⌿") (= tv "\\") (= tv "⍀"))
-                    (collect-segments-loop
-                      tokens
-                      (+ i 1)
-                      (append acc {:kind "fn" :node (list :fn-glyph tv)}))
+                    (let
+                      ((next-i (+ i 1)))
+                      (let
+                        ((next-tok (if (< next-i n) (nth tokens next-i) nil)))
+                        (let
+                          ((mod (if (and next-tok (= (tok-type next-tok) :glyph) (or (= (get next-tok :value) "⍨") (= (get next-tok :value) "¨"))) (get next-tok :value) nil))
+                            (base-fn-node (list :fn-glyph tv)))
+                          (let
+                            ((node (if mod (list :derived-fn mod base-fn-node) base-fn-node))
+                              (advance (if mod 2 1)))
+                            (collect-segments-loop
+                              tokens
+                              (+ i advance)
+                              (append acc {:kind "fn" :node node}))))))
                     (collect-segments-loop tokens (+ i 1) acc)))
                 (true (collect-segments-loop tokens (+ i 1) acc))))
             (true (collect-segments-loop tokens (+ i 1) acc))))))))