spec: vector primitive — complete type signatures in spec/primitives.sx

All 10 vector primitives now have :as type annotations on every parameter,
:returns types, and :doc strings. make-vector gains optional fill annotation;
vector uses :rest for its variadic args; vector-ref/set! document bounds error.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

plans/agent-briefings/primitives-loop.md

@@ -54,7 +54,9 @@ Steps:
       primitives in `hosts/ocaml/sx_primitives.ml` (or equivalent); wire into evaluator.
       Note: Vector type + most prims were already present; added bounds-checked vector-ref/set!
       and optional start/end to vector-copy. 10/10 vector tests pass (r7rs suite).
-- [ ] Spec: add vector entries to `spec/primitives.sx` with type signatures and descriptions.
+- [x] Spec: add vector entries to `spec/primitives.sx` with type signatures and descriptions.
+      All 10 vector primitives now have :as type annotations, :returns, and :doc strings.
+      make-vector: optional fill param; vector-copy: optional start/end (done prev step).
 - [ ] JS bootstrapper: implement vectors in `hosts/javascript/platform.js` (or equivalent);
       ensure `sx-browser.js` rebuild picks them up.
 - [ ] Tests: 40+ tests in `spec/tests/test-vectors.sx` covering construction, ref, set!,
@@ -196,5 +198,6 @@ Brief each language's loop agent (or do inline) after rebasing their branch onto
 
 _Newest first._
 
+- 2026-04-25: Phase 1 spec step done — all 10 vector primitives in spec/primitives.sx have full :as type annotations, :returns, :doc; make-vector optional fill param added.
 - 2026-04-25: Phase 1 OCaml step done — bounds-checked vector-ref/set!, vector-copy now accepts optional start/end, spec/primitives.sx doc updated. 10/10 r7rs vector tests pass, 4747 total (394 pre-existing hs-upstream fails unchanged).
 - 2026-04-25: Phase 0 complete — stopped CL/APL/Ruby/Tcl loops (all 4 idle at shell); confirmed E38 (tokenizer :end/:line) and E39 (WebWorker stub) both have implementation commits.