feat: revamp DeepSeek v4 model handling

- replace legacy DeepSeek ids with the new deepseek-v4 model family\n- move thinking control to request parameters and preserve assistant reasoning content\n- switch history split to IGNORE transcript injection and map upload auth failures to 401\n- update admin defaults, API docs, samples, and tests for the new model scheme

tests/raw_stream_samples/content-filter-trigger-20260405-jwt3/meta.json

@@ -2,7 +2,7 @@
   "sample_id": "content-filter-trigger-20260405-jwt3",
   "captured_at_utc": "2026-04-04T16:28:52Z",
   "request": {
-    "model": "deepseek-reasoner-search",
+    "model": "deepseek-v4-pro-search",
     "stream": true,
     "messages": [
       {

tests/raw_stream_samples/guangzhou-weather-reasoner-search-20260404/meta.json

@@ -2,7 +2,7 @@
   "sample_id": "guangzhou-weather-reasoner-search-20260404",
   "captured_at_utc": "2026-04-04T16:01:27Z",
   "request": {
-    "model": "deepseek-reasoner-search",
+    "model": "deepseek-v4-pro-search",
     "stream": true,
     "messages": [
       {

tests/raw_stream_samples/markdown-format-example-20260405-spacefix/meta.json

@@ -9,7 +9,7 @@
         "role": "user"
       }
     ],
-    "model": "deepseek-reasoner-search",
+    "model": "deepseek-v4-pro-search",
     "stream": true
   },
   "capture": {

tests/raw_stream_samples/markdown-format-example-20260405/meta.json

@@ -9,7 +9,7 @@
         "role": "user"
       }
     ],
-    "model": "deepseek-reasoner-search",
+    "model": "deepseek-v4-pro-search",
     "stream": true
   },
   "capture": {

tests/scripts/capture-raw-stream-sample.sh

@@ -7,7 +7,7 @@ cd "$ROOT_DIR"
 CONFIG_PATH="${1:-config.json}"
 SAMPLE_ID="${2:-capture-$(date -u +%Y%m%dT%H%M%SZ)}"
 QUESTION="${3:-广州天气}"
-MODEL="${4:-deepseek-reasoner-search}"
+MODEL="${4:-deepseek-v4-pro-search}"
 API_KEY="${5:-}"
 ADMIN_KEY="${DS2API_ADMIN_KEY:-admin}"