mk: phase 3 — run* / run / reify, 18 new tests

run.sx: reify-name builds canonical "_.N" symbols; reify-s walks a term
left-to-right and assigns each unbound var its index in the discovery
order; reify combines the two with two walk* passes. run-n is the
runtime defmacro: binds the query var, takes ≤ n stream answers, reifies
each. run* and run are sugar around it.

First classic miniKanren tests green:
  (run* q (== q 1))                              → (1)
  (run* q (conde ((== q 1)) ((== q 2))))         → (1 2)
  (run* q (fresh (x y) (== q (list x y))))       → ((_.0 _.1))

128/128 cumulative.

plans/minikanren-on-sx.md

@@ -86,15 +86,18 @@ Key semantic mappings:
 - [x] Tests: basic goal composition, backtracking, interleaving (110 cumulative)
 
 ### Phase 3 — run + reification
-- [ ] `run*` `goal` → list of all answers (reified)
-- [ ] `run n` `goal` → list of first n answers
-- [ ] `reify` `term` `subst` → replace unbound vars with `_0`, `_1`, ... names
-- [ ] `reify-s` → builds reification substitution for naming unbound vars consistently
-- [ ] `fresh` with multiple variables: `(fresh (x y z) goal)` sugar
-- [ ] Query variable conventions: `q` as canonical query variable
-- [ ] Tests: classic miniKanren programs — `(run* q (== q 1))` → `(1)`,
+- [x] `run*` `goal` → list of all answers (reified). defmacro: bind q-name as
+      fresh var, conj goals, take all from stream, reify each.
+- [x] `run n` `goal` → list of first n answers (defmacro; n = -1 means all)
+- [x] `reify` `term` `subst` → walk* + build reification subst + walk* again
+- [x] `reify-s` → maps each unbound var (in left-to-right walk order) to a
+      `_.N` symbol via `(make-symbol (str "_." n))`
+- [x] `fresh` with multiple variables — already shipped Phase 2B.
+- [x] Query variable conventions: `q` as canonical query variable (matches TRS)
+- [x] Tests: classic miniKanren programs — `(run* q (== q 1))` → `(1)`,
       `(run* q (conde ((== q 1)) ((== q 2))))` → `(1 2)`,
-      Peano arithmetic, `appendo` preview
+      `(run* q (fresh (x y) (== q (list x y))))` → `((_.0 _.1))`. Peano +
+      `appendo` deferred to Phase 4.
 
 ### Phase 4 — standard relations
 - [ ] `appendo` `l` `s` `ls` — list append, runs forwards and backwards
@@ -148,6 +151,12 @@ _(none yet)_
 
 _Newest first._
 
+- **2026-05-07** — **Phase 3 done** (run + reification): `lib/minikanren/run.sx` (~28 lines).
+  `reify`/`reify-s`/`reify-name` for canonical `_.N` rendering of unbound vars in
+  left-to-right occurrence order; `run*` / `run` / `run-n` defmacros. 18 new tests
+  in `tests/run.sx`, including the **first classic miniKanren tests green**:
+  `(run* q (== q 1))` → `(1)`; `(run* q (fresh (x y) (== q (list x y))))` →
+  `((_.0 _.1))`. 128/128 cumulative.
 - **2026-05-07** — **Phase 2 piece D + done** (`condu` / `onceo`): `lib/minikanren/condu.sx`.
   Both are commitment forms: `onceo` is `(stream-take 1 ...)`; `condu` walks clauses
   and commits the first one whose head produces an answer. 10 tests in `tests/condu.sx`,