Add deps and engine test specs, bootstrap engine to Python

New test specs (test-deps.sx: 33 tests, test-engine.sx: 37 tests) covering
component dependency analysis and engine pure functions. All 6 spec modules
now have formal SX tests: eval (81), parser (39), router (18), render (23),
deps (33), engine (37) = 231 total.

- Add engine as spec module in bootstrap_py.py (alongside deps)
- Add primitive aliases (trim, replace, parse_int, upper) for engine functions
- Fix parse-int to match JS parseInt semantics (strip trailing non-digits)
- Regenerate sx_ref.py with --spec-modules deps,engine
- Update all three test runners (run.js, run.py, sx-test-runner.js)
- Add Dependencies and Engine nav items and testing page entries
- Wire deps-source/engine-source through testing overview UI

Node.js: 231/231 pass. Python: 226/231 (5 pre-existing parser/router gaps).

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

sx/sx/nav-data.sx

@@ -113,6 +113,8 @@
   (dict :label "Parser" :href "/testing/parser")
   (dict :label "Router" :href "/testing/router")
   (dict :label "Renderer" :href "/testing/render")
+  (dict :label "Dependencies" :href "/testing/deps")
+  (dict :label "Engine" :href "/testing/engine")
   (dict :label "Runners" :href "/testing/runners")))
 
 (define isomorphism-nav-items (list

sx/sx/testing.sx

@@ -6,7 +6,7 @@
 ;; Overview page
 ;; ---------------------------------------------------------------------------
 
-(defcomp ~testing-overview-content (&key server-results framework-source eval-source parser-source router-source render-source)
+(defcomp ~testing-overview-content (&key server-results framework-source eval-source parser-source router-source render-source deps-source engine-source)
   (~doc-page :title "Testing"
     (div :class "space-y-8"
 
@@ -35,6 +35,8 @@
     +-- test-parser.sx         39 tests: tokenizer, parser, serializer
     +-- test-router.sx         18 tests: route matching + param extraction
     +-- test-render.sx         23 tests: HTML rendering + components
+    +-- test-deps.sx           33 tests: dependency analysis + IO detection
+    +-- test-engine.sx         37 tests: trigger/swap/retry parsing
 
 Runners:
     run.js                     Node.js — injects platform fns, runs specs
@@ -51,7 +53,9 @@ Platform functions (5 total):
 Per-spec platform functions:
     parser:  sx-parse, sx-serialize, make-symbol, make-keyword, ...
     router:  (none — pure spec, uses bootstrapped functions)
-    render:  render-html (wraps parse + render-to-html)")))
+    render:  render-html (wraps parse + render-to-html)
+    deps:    test-env (returns current evaluation environment)
+    engine:  (none — pure spec, uses bootstrapped functions)")))
 
       ;; Server results
       (when server-results
@@ -86,6 +90,8 @@ Per-spec platform functions:
         (textarea :id "test-spec-parser" :style "display:none" parser-source)
         (textarea :id "test-spec-router" :style "display:none" router-source)
         (textarea :id "test-spec-render" :style "display:none" render-source)
+        (textarea :id "test-spec-deps" :style "display:none" deps-source)
+        (textarea :id "test-spec-engine" :style "display:none" engine-source)
         (script :src (asset-url "/scripts/sx-test-runner.js")))
 
       ;; Test spec index
@@ -107,7 +113,15 @@ Per-spec platform functions:
           (a :href "/testing/render" :class "block rounded-lg border border-stone-200 p-5 hover:border-violet-300 hover:bg-violet-50 transition-colors"
             (h3 :class "font-semibold text-stone-800" "Renderer")
             (p :class "text-sm text-stone-500" "23 tests — elements, attributes, void elements, fragments, escaping, control flow, components")
-            (p :class "text-xs text-violet-600 mt-1" "test-render.sx"))))
+            (p :class "text-xs text-violet-600 mt-1" "test-render.sx"))
+          (a :href "/testing/deps" :class "block rounded-lg border border-stone-200 p-5 hover:border-violet-300 hover:bg-violet-50 transition-colors"
+            (h3 :class "font-semibold text-stone-800" "Dependencies")
+            (p :class "text-sm text-stone-500" "33 tests — scan-refs, transitive-deps, components-needed, IO detection, purity classification")
+            (p :class "text-xs text-violet-600 mt-1" "test-deps.sx"))
+          (a :href "/testing/engine" :class "block rounded-lg border border-stone-200 p-5 hover:border-violet-300 hover:bg-violet-50 transition-colors"
+            (h3 :class "font-semibold text-stone-800" "Engine")
+            (p :class "text-sm text-stone-500" "37 tests — parse-time, trigger specs, swap specs, retry logic, param filtering")
+            (p :class "text-xs text-violet-600 mt-1" "test-engine.sx"))))
 
       ;; What it proves
       (div :class "rounded-lg border border-blue-200 bg-blue-50 p-5 space-y-3"