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>

shared/sx/tests/run.py

@@ -141,6 +141,8 @@ SPECS = {
     "parser": {"file": "test-parser.sx", "needs": ["sx-parse"]},
     "router": {"file": "test-router.sx", "needs": []},
     "render": {"file": "test-render.sx", "needs": ["render-html"]},
+    "deps":   {"file": "test-deps.sx",   "needs": []},
+    "engine": {"file": "test-engine.sx", "needs": []},
 }
 
 REF_DIR = os.path.join(_HERE, "..", "ref")
@@ -269,6 +271,62 @@ def _load_router_from_bootstrap(env):
         eval_file("router.sx", env)
 
 
+def _load_deps_from_bootstrap(env):
+    """Load deps functions from the bootstrapped sx_ref.py."""
+    try:
+        from shared.sx.ref.sx_ref import (
+            scan_refs,
+            scan_components_from_source,
+            transitive_deps,
+            compute_all_deps,
+            components_needed,
+            page_component_bundle,
+            page_css_classes,
+            scan_io_refs,
+            transitive_io_refs,
+            compute_all_io_refs,
+            component_pure_p,
+        )
+        env["scan-refs"] = scan_refs
+        env["scan-components-from-source"] = scan_components_from_source
+        env["transitive-deps"] = transitive_deps
+        env["compute-all-deps"] = compute_all_deps
+        env["components-needed"] = components_needed
+        env["page-component-bundle"] = page_component_bundle
+        env["page-css-classes"] = page_css_classes
+        env["scan-io-refs"] = scan_io_refs
+        env["transitive-io-refs"] = transitive_io_refs
+        env["compute-all-io-refs"] = compute_all_io_refs
+        env["component-pure?"] = component_pure_p
+        env["test-env"] = lambda: env
+    except ImportError:
+        eval_file("deps.sx", env)
+        env["test-env"] = lambda: env
+
+
+def _load_engine_from_bootstrap(env):
+    """Load engine pure functions from the bootstrapped sx_ref.py."""
+    try:
+        from shared.sx.ref.sx_ref import (
+            parse_time,
+            parse_trigger_spec,
+            default_trigger,
+            parse_swap_spec,
+            parse_retry_spec,
+            next_retry_ms,
+            filter_params,
+        )
+        env["parse-time"] = parse_time
+        env["parse-trigger-spec"] = parse_trigger_spec
+        env["default-trigger"] = default_trigger
+        env["parse-swap-spec"] = parse_swap_spec
+        env["parse-retry-spec"] = parse_retry_spec
+        env["next-retry-ms"] = next_retry_ms
+        env["filter-params"] = filter_params
+    except ImportError:
+        eval_file("engine.sx", env)
+
+
 def main():
     global passed, failed, test_num
 
@@ -306,6 +364,10 @@ def main():
             # Load prerequisite spec modules
             if spec_name == "router":
                 _load_router_from_bootstrap(env)
+            if spec_name == "deps":
+                _load_deps_from_bootstrap(env)
+            if spec_name == "engine":
+                _load_engine_from_bootstrap(env)
 
             print(f"# --- {spec_name} ---")
             eval_file(spec["file"], env)