Phase 7a: affinity annotations + fix parser escape sequences

Add :affinity :client/:server/:auto annotations to defcomp, with
render-target function combining affinity + IO analysis. Includes
spec (eval.sx, deps.sx), tests, Python evaluator, and demo page.

Fix critical bug: Python SX parser _ESCAPE_MAP was missing \r and \0,
causing bootstrapped JS parser to treat 'r' as whitespace — breaking
all client-side SX parsing. Also add \0 to JS string emitter and
fix serializer round-tripping for \r and \0.

Reserved word escaping: bootstrappers now auto-append _ to identifiers
colliding with JS/Python reserved words (e.g. default → default_,
final → final_), so the spec never needs to avoid host language keywords.

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

sx/sxc/pages/docs.sx

@@ -479,6 +479,18 @@
     :stream-message stream-message
     :stream-time stream-time))
 
+(defpage affinity-demo
+  :path "/isomorphism/affinity"
+  :auth :public
+  :layout (:sx-section
+    :section "Isomorphism"
+    :sub-label "Isomorphism"
+    :sub-href "/isomorphism/"
+    :sub-nav (~section-nav :items isomorphism-nav-items :current "Affinity")
+    :selected "Affinity")
+  :data (affinity-demo-data)
+  :content (~affinity-demo-content :components components))
+
 ;; Wildcard must come AFTER specific routes (first-match routing)
 (defpage isomorphism-page
   :path "/isomorphism/<slug>"

sx/sxc/pages/helpers.py

@@ -27,6 +27,7 @@ def _register_sx_helpers() -> None:
         "run-spec-tests": _run_spec_tests,
         "run-modular-tests": _run_modular_tests,
         "streaming-demo-data": _streaming_demo_data,
+        "affinity-demo-data": _affinity_demo_data,
     })
 
 
@@ -318,6 +319,8 @@ def _bundle_analyzer_data() -> dict:
                 comp_details.append({
                     "name": comp_name,
                     "is-pure": is_pure,
+                    "affinity": val.affinity,
+                    "render-target": val.render_target,
                     "io-refs": sorted(val.io_refs),
                     "deps": sorted(val.deps),
                     "source": source,
@@ -875,3 +878,30 @@ async def _streaming_demo_data():
         "stream-message": "Model inference completed in ~5 seconds",
         "stream-time": datetime.now(timezone.utc).isoformat(timespec="seconds"),
     }
+
+
+def _affinity_demo_data() -> dict:
+    """Return affinity analysis for the demo components."""
+    from shared.sx.jinja_bridge import get_component_env
+    from shared.sx.types import Component
+
+    env = get_component_env()
+    demo_names = [
+        "~aff-demo-auto",
+        "~aff-demo-client",
+        "~aff-demo-server",
+        "~aff-demo-io-auto",
+        "~aff-demo-io-client",
+    ]
+    components = []
+    for name in demo_names:
+        val = env.get(name)
+        if isinstance(val, Component):
+            components.append({
+                "name": name,
+                "affinity": val.affinity,
+                "render-target": val.render_target,
+                "io-refs": sorted(val.io_refs),
+                "is-pure": val.is_pure,
+            })
+    return {"components": components}