fix(chat): store bridge messages/tools as raw JSON to prevent double-escape corruption on agentic_resume

bridge_save was wrapping messages and tools_json with json_safe() before
storing them as string fields. Since both are already well-formed JSON arrays
containing double quotes, json_safe added a second escape layer. agentic_resume
then called json_get() which stripped only one layer, leaving the messages array
corrupted before it was passed back into agentic_loop.

Fix: store messages as messages_raw and tools_json as tools_raw as inline raw
JSON values (unquoted), and read them back with json_get_raw. Backward
compatibility: fall back to the old string-escaped fields if the raw fields are
absent, so sessions saved before this fix can still be resumed.

Also fixes write_file returning a pre-escaped literal instead of calling
json_safe consistently with every other tool result.

chat.el

@@ -387,7 +387,7 @@ fn dispatch_tool(tool_name: String, tool_input: String) -> String {
         let path: String = json_get(tool_input, "path")
         let content: String = json_get(tool_input, "content")
         fs_write(path, content)
-        return "{\\\"ok\\\":true}"
+        return json_safe("{\"ok\":true}")
     }
     if str_eq(tool_name, "web_get") {
         let url: String = json_get(tool_input, "url")
@@ -766,10 +766,14 @@ fn agentic_loop(session_id: String, model: String, safe_sys: String, tools_json:
 // stored `messages` already includes the assistant turn that requested the tool, so
 // resume just appends the client's tool_result for `tool_use_id`.
 fn bridge_save(session_id: String, model: String, safe_sys: String, tools_json: String, messages: String, tools_log: String, tool_use_id: String) -> Bool {
+    // messages and tools_json are already well-formed JSON arrays; embed them as raw
+    // JSON values (not string-escaped) so the round-trip through state_get/json_get_raw
+    // never corrupts nested quotes. Scalar strings (model, safe_sys, tools_log,
+    // tool_use_id) stay as string fields via json_safe as before.
     let blob: String = "{\"model\":\"" + json_safe(model) + "\""
         + ",\"safe_sys\":\"" + json_safe(safe_sys) + "\""
-        + ",\"tools_json\":\"" + json_safe(tools_json) + "\""
-        + ",\"messages\":\"" + json_safe(messages) + "\""
+        + ",\"messages_raw\":" + messages
+        + ",\"tools_raw\":" + tools_json
         + ",\"tools_log\":\"" + json_safe(tools_log) + "\""
         + ",\"tool_use_id\":\"" + json_safe(tool_use_id) + "\"}"
     state_set("mcp_bridge:" + session_id, blob)
@@ -789,8 +793,12 @@ fn agentic_resume(session_id: String, tool_use_id: String, content: String) -> S
 
     let model: String = json_get(blob, "model")
     let safe_sys: String = json_get(blob, "safe_sys")
-    let tools_json: String = json_get(blob, "tools_json")
-    let messages: String = json_get(blob, "messages")
+    // messages_raw and tools_raw are embedded as raw JSON (not string-escaped);
+    // fall back to legacy string-escaped fields for sessions saved before this fix.
+    let messages: String = json_get_raw(blob, "messages_raw")
+    let messages: String = if str_eq(messages, "") { json_get(blob, "messages") } else { messages }
+    let tools_json: String = json_get_raw(blob, "tools_raw")
+    let tools_json: String = if str_eq(tools_json, "") { json_get(blob, "tools_json") } else { tools_json }
     let tools_log: String = json_get(blob, "tools_log")
     let saved_use_id: String = json_get(blob, "tool_use_id")