Update sx-docs: add deps spec to viewer, mark Phase 1 complete

Add deps.sx to the spec navigator in sx-docs (nav-data, specs page).
Update isomorphic architecture plan to show Phase 1 as complete with
link to the canonical spec at /specs/deps.

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

sx/sx/specs.sx

@@ -179,7 +179,10 @@ boot.sx             depends on: cssx, orchestration, adapter-dom, render
 
 ;; Extensions (optional — loaded only when target requests them)
 continuations.sx    depends on: eval (optional)
-callcc.sx           depends on: eval (optional)")))
+callcc.sx           depends on: eval (optional)
+
+;; Spec modules (optional — loaded via --spec-modules)
+deps.sx             depends on: eval (optional)")))
 
       (div :class "space-y-3"
         (h2 :class "text-2xl font-semibold text-stone-800" "Extensions")