refactor: identify and freeze messages at creation

scripts/type-equiv.manifest.json

@@ -14,17 +14,17 @@
     {
       "doc": "docs/core-data-structures/core.md",
       "symbol": "AssistantProvenance",
-      "source": "packages/llm/llm/src/types.ts"
+      "source": "packages/llm/llm/src/message.ts"
     },
     {
       "doc": "docs/core-data-structures/core.md",
       "symbol": "Message",
-      "source": "packages/llm/llm/src/types.ts"
+      "source": "packages/llm/llm/src/message.ts"
     },
     {
       "doc": "docs/core-data-structures/core.md",
       "symbol": "MessageSourceMap",
-      "source": "packages/llm/llm/src/types.ts"
+      "source": "packages/llm/llm/src/message.ts"
     },
     {
       "doc": "docs/core-data-structures/core.md",
@@ -101,16 +101,6 @@
       "symbol": "SendOptions",
       "source": "packages/core/agent/src/types.ts"
     },
-    {
-      "doc": "docs/core-data-structures/core.md",
-      "symbol": "AgentMessageId",
-      "source": "packages/core/agent/src/types.ts"
-    },
-    {
-      "doc": "docs/core-data-structures/core.md",
-      "symbol": "AgentMessage",
-      "source": "packages/core/agent/src/types.ts"
-    },
     {
       "doc": "docs/core-data-structures/core.md",
       "symbol": "CancelOptions",
@@ -320,8 +310,8 @@
     },
     {
       "doc": "docs/core-data-structures/session.md",
-      "symbol": "UserMessageData",
-      "source": "packages/core/session/src/types.ts"
+      "symbol": "UserMessage",
+      "source": "packages/llm/llm/src/message.ts"
     },
     {
       "doc": "docs/core-data-structures/session.md",