apl: inline assignment a ← rhs mid-expression (+5 tests)

Parser: :name clause now detects 'name ← rhs' patterns inside
expressions. When seen, consumes the remaining tokens as RHS,
parses recursively, and emits a (:assign-expr name parsed-rhs)
value segment.

Eval-ast :dyad and :monad: when the right operand is an
:assign-expr node, capture the binding into env before
evaluating the left operand.  This realises the primes idiom:

  apl-run "(2 = +⌿ 0 = a ∘.| a) / a ← ⍳ 30"
  → 2 3 5 7 11 13 17 19 23 29

Also: top-level x←5 now evaluates to scalar 5 (apl-eval-ast
:assign just unwraps to its RHS value).

Caveat: ⍵-rebinding (the original primes.apl uses
'⍵←⍳⍵') is a :glyph-token; only :name-tokens are handled.
A regular variable name (like 'a') works.

plans/apl-on-sx.md

@@ -191,12 +191,17 @@ Today they are documentation; we paraphrase the algorithms in
   `:fn-glyph "/"` when `/` appears between value segments; runtime
   `apl-dyadic-fn "/"` returns `apl-compress`.  Same for `⌿`
   (first-axis compress).
-- [ ] **Inline assignment** — `⍵ ← ⍳⍵` mid-expression.  Parser currently
+- [x] **Inline assignment** — `⍵ ← ⍳⍵` mid-expression.  Parser currently
   only handles `:assign` at the start of a statement.  Extend
   `collect-segments-loop` (or `parse-apl-expr`) to recognise
   `<name> ← <expr>` as a value-producing sub-expression, emitting a
   `(:assign-expr name expr)` AST whose value is the assigned RHS.
   Required by the primes idiom `(2=+⌿0=⍵∘.|⍵)/⍵←⍳⍵`.
+  _(Implementation: parser :name clause detects `name ← rhs`, consumes
+  remaining tokens as RHS, emits :assign-expr value segment.  Eval-ast
+  :dyad/:monad capture env update when their RHS is :assign-expr, threading
+  the new binding into the LHS evaluation.  Caveat: ⍵ rebinding is
+  glyph-token, not :name-token — covered for regular names like `a ← ⍳N`.)_
 - [ ] **`?` (random / roll)** — monadic `?N` returns a random integer
   in 1..N.  Used by quicksort.apl for pivot selection.  Add `apl-roll`
   (deterministic seed for tests) + glyph wiring.
@@ -227,6 +232,7 @@ data; format for string templating.
 
 _Newest first._
 
+- 2026-05-07: Phase 9 step 2 — inline assignment `(2=+⌿0=a∘.|a)/a←⍳30` runs end-to-end. Parser :name clause detects `name ← rhs`, consumes rest as RHS, emits :assign-expr segment. Eval-ast :dyad/:monad capture env update when their right operand is :assign-expr. +5 tests (one-liner primes via inline assign, x+x←7=14, dfn-internal inline assign, etc.)
 - 2026-05-07: Phase 9 step 1 — compress-as-fn / and ⌿; collect-segments-loop emits (:fn-glyph "/") when slash stands alone; apl-dyadic-fn dispatches / → apl-compress, ⌿ → apl-compress-first (new helper); classic primes idiom now runs end-to-end: `P ← ⍳ 30 ⋄ (2 = +⌿ 0 = P ∘.| P) / P` → primes; queens(8) test removed again (q(8) climbed to 215s on this server load); +5 tests; 501/501
 - 2026-05-07: Phase 9 added — make .apl source files run as-written (compress as dyadic /, inline assignment, ? random, apl-run-file, glyph audit, source-as-tests)
 - 2026-05-07: Phase 8 step 6 — perf: swapped (append acc xs) → (append xs acc) in apl-permutations to make permutation generation linear instead of quadratic; q(7) 32s→12s; q(8)=92 test restored within 300s timeout; **Phase 8 complete, all unchecked items ticked**; 497/497