Add header and event detail pages, fix copyright, rename essay

- Detail pages for all 18 HTTP headers with descriptions, example usage,
  direction badges (request/response/both), and live demos for SX-Prompt,
  SX-Trigger, SX-Retarget
- Detail pages for all 10 DOM events with descriptions, example usage,
  and live demos for beforeRequest, afterSettle, responseError,
  validationFailed
- Header and event table rows now link to their detail pages
- Fix copyright symbol on home page (was literal \u00a9, now actual ©)
- Rename "Godel, Escher, Bach" essay to "Strange Loops" with updated summary
- Remove duplicate script injection from bootstrapper page

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

sx/sxc/pages/docs.sx

@@ -115,6 +115,43 @@
       :handler-code attr-handler
       :wire-placeholder-id attr-wire-id)))
 
+(defpage reference-header-detail
+  :path "/reference/headers/<slug>"
+  :auth :public
+  :layout (:sx-section
+    :section "Reference"
+    :sub-label "Reference"
+    :sub-href "/reference/"
+    :sub-nav (~section-nav :items reference-nav-items :current "Headers")
+    :selected "Headers")
+  :data (header-detail-data slug)
+  :content (if header-not-found
+    (~reference-attr-not-found :slug slug)
+    (~reference-header-detail-content
+      :title header-title
+      :direction header-direction
+      :description header-description
+      :example-code header-example
+      :demo header-demo)))
+
+(defpage reference-event-detail
+  :path "/reference/events/<slug>"
+  :auth :public
+  :layout (:sx-section
+    :section "Reference"
+    :sub-label "Reference"
+    :sub-href "/reference/"
+    :sub-nav (~section-nav :items reference-nav-items :current "Events")
+    :selected "Events")
+  :data (event-detail-data slug)
+  :content (if event-not-found
+    (~reference-attr-not-found :slug slug)
+    (~reference-event-detail-content
+      :title event-title
+      :description event-description
+      :example-code event-example
+      :demo event-demo)))
+
 ;; ---------------------------------------------------------------------------
 ;; Protocols section
 ;; ---------------------------------------------------------------------------

sx/sxc/pages/helpers.py

@@ -16,6 +16,8 @@ def _register_sx_helpers() -> None:
         "primitives-data": _primitives_data,
         "reference-data": _reference_data,
         "attr-detail-data": _attr_detail_data,
+        "header-detail-data": _header_detail_data,
+        "event-detail-data": _event_detail_data,
         "read-spec-file": _read_spec_file,
         "bootstrapper-data": _bootstrapper_data,
     })
@@ -39,7 +41,7 @@ def _reference_data(slug: str) -> dict:
     from content.pages import (
         REQUEST_ATTRS, BEHAVIOR_ATTRS, SX_UNIQUE_ATTRS,
         REQUEST_HEADERS, RESPONSE_HEADERS,
-        EVENTS, JS_API, ATTR_DETAILS,
+        EVENTS, JS_API, ATTR_DETAILS, HEADER_DETAILS,
     )
 
     if slug == "attributes":
@@ -63,18 +65,22 @@ def _reference_data(slug: str) -> dict:
     elif slug == "headers":
         return {
             "req-headers": [
-                {"name": n, "value": v, "desc": d}
+                {"name": n, "value": v, "desc": d,
+                 "href": f"/reference/headers/{n}" if n in HEADER_DETAILS else None}
                 for n, v, d in REQUEST_HEADERS
             ],
             "resp-headers": [
-                {"name": n, "value": v, "desc": d}
+                {"name": n, "value": v, "desc": d,
+                 "href": f"/reference/headers/{n}" if n in HEADER_DETAILS else None}
                 for n, v, d in RESPONSE_HEADERS
             ],
         }
     elif slug == "events":
+        from content.pages import EVENT_DETAILS
         return {
             "events-list": [
-                {"name": n, "desc": d}
+                {"name": n, "desc": d,
+                 "href": f"/reference/events/{n}" if n in EVENT_DETAILS else None}
                 for n, d in EVENTS
             ],
         }
@@ -190,3 +196,42 @@ def _attr_detail_data(slug: str) -> dict:
         "attr-demo": SxExpr(f"(~{demo_name})") if demo_name else None,
         "attr-wire-id": wire_id,
     }
+
+
+def _header_detail_data(slug: str) -> dict:
+    """Return header detail data for a specific header slug."""
+    from content.pages import HEADER_DETAILS
+    from shared.sx.helpers import SxExpr
+
+    detail = HEADER_DETAILS.get(slug)
+    if not detail:
+        return {"header-not-found": True}
+
+    demo_name = detail.get("demo")
+    return {
+        "header-not-found": None,
+        "header-title": slug,
+        "header-direction": detail["direction"],
+        "header-description": detail["description"],
+        "header-example": detail.get("example"),
+        "header-demo": SxExpr(f"(~{demo_name})") if demo_name else None,
+    }
+
+
+def _event_detail_data(slug: str) -> dict:
+    """Return event detail data for a specific event slug."""
+    from content.pages import EVENT_DETAILS
+    from shared.sx.helpers import SxExpr
+
+    detail = EVENT_DETAILS.get(slug)
+    if not detail:
+        return {"event-not-found": True}
+
+    demo_name = detail.get("demo")
+    return {
+        "event-not-found": None,
+        "event-title": slug,
+        "event-description": detail["description"],
+        "event-example": detail.get("example"),
+        "event-demo": SxExpr(f"(~{demo_name})") if demo_name else None,
+    }