test: 16 dynamic PRG tests — all new syntax works in FRB/runtime

Verifies every Five extension works in dynamic compilation:
- Multi-return (RETURN a,b + a,b := Func())
- DEFER (Go defer in PRG)
- Slice (a[2:4])
- Channel operators (ch <- val, <- ch)
- SPAWN / LAUNCH / GOROUTINE
- WATCH (channel multiplexing)
- ASYNC / AWAIT
- WITH TIMEOUT
- Nil-safe (?:)
- f-string interpolation
- CONST block
- PARALLEL FOR
- IMPORT + pkg.Func() (Go direct call)
- obj:Method() (Go object bridge)
- MacroEval (runtime expression evaluation)

All 16 tests PASS — dynamic PRG has full feature parity.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

docs/.pdca-status.json

@@ -1,6 +1,6 @@
 {
   "version": "2.0",
-  "lastUpdated": "2026-03-31T01:11:37.627Z",
+  "lastUpdated": "2026-03-31T01:15:54.989Z",
   "activeFeatures": [
     "hbrt",
     "hbrtl",
@@ -32,9 +32,9 @@
       "documents": {},
       "timestamps": {
         "started": "2026-03-27T09:33:04.512Z",
-        "lastUpdated": "2026-03-31T01:11:37.627Z"
+        "lastUpdated": "2026-03-31T01:15:54.989Z"
       },
-      "lastFile": "/mnt/d/charles/five/hbrt/shutdown_test.go"
+      "lastFile": "/mnt/d/charles/five/hbrt/dynamic_syntax_test.go"
     },
     "hbrtl": {
       "phase": "do",
@@ -266,7 +266,7 @@
   "session": {
     "startedAt": "2026-03-27T06:06:49.620Z",
     "onboardingCompleted": false,
-    "lastActivity": "2026-03-31T01:11:37.627Z"
+    "lastActivity": "2026-03-31T01:15:54.989Z"
   },
   "history": [
     {
@@ -5368,6 +5368,12 @@
       "feature": "hbrt",
       "phase": "do",
       "action": "updated"
+    },
+    {
+      "timestamp": "2026-03-31T01:15:54.989Z",
+      "feature": "hbrt",
+      "phase": "do",
+      "action": "updated"
     }
   ]
 }