refactor(platforms): 学习流程下沉到平台层，engine 只保留编排

SessionExpired 移到 platforms/errors.py；旧版流程（_study_builtin）搬到 jspx.py，新版 SPA 流程（run_study_course + 视频）搬到 study.py；engine.py 只剩账号级编排，不再 import 具体平台；routes/quiz 去掉平台 star import，session/dump_cookies 缺失时明确报错。顺带修复学习链路三处未定义全局名（jspx/study/quiz）。

src/study_tool/routes/misc.py

@@ -8,12 +8,11 @@ from study_tool.webapp import app
 from study_tool import store
 from study_tool.capture import *
 from study_tool.config import *
-from study_tool.engine import *
+from study_tool.engine import study_worker
 from study_tool.models import *
 from study_tool.platforms import registry
-from study_tool.platforms.jspx import *
-from study_tool.platforms.study import *
-from study_tool.runtime import RUNS, RUNS_LOCK, log
+from study_tool.platforms.errors import SessionExpired
+from study_tool.runtime import RUNS, RUNS_LOCK, log, set_state
 from study_tool.settings_store import load_settings
 
 # ------------------------------------------------------------------ 平台
@@ -74,10 +73,13 @@ def api_courses(b: CookiesIn):
         return JSONResponse({"ok": False, "code": "no_platform",
                              "error": "平台「%s」还没有实现刷新课程，请先在 platforms/ 里补上"
                                       % b.platform}, status_code=200)
-    s = (pf.session or new_session)(b.cookies)
+    if pf.session is None:
+        return JSONResponse({"ok": False, "code": "no_platform",
+                             "error": "平台「%s」还没有实现 session" % b.platform}, status_code=200)
+    s = pf.session(b.cookies)
     if not s.cookies:
         return JSONResponse({"ok": False, "code": "no_cookie",
-                             "error": "保存的 cookie 全部被过滤（domain 不含 dgjy），请重新登录"},
+                             "error": "保存的 cookie 全部被过滤（站点域名不匹配），请重新登录"},
                             status_code=200)
     try:
         courses = pf.list_courses(s)
@@ -96,7 +98,7 @@ def api_courses(b: CookiesIn):
     return {"ok": True, "courses": courses, "user": user,
             "in_study": len([c for c in courses if c["in_study"]]),
             # 补 jspx 会话时 cookie 会换新（JSESSIONID/route），回传让前端写回
-            "cookies": (pf.dump_cookies or dump_cookies)(s)}
+            "cookies": (pf.dump_cookies(s) if pf.dump_cookies else [])}
 
 
 @app.post("/api/discover")
@@ -105,10 +107,13 @@ def api_discover(b: DiscoverIn):
     if pf is None or pf.discover is None:
         return JSONResponse({"ok": False, "code": "no_platform",
                              "error": "平台「%s」还没有实现课程发现" % b.platform}, status_code=200)
-    s = (pf.session or new_session)(b.cookies)
+    if pf.session is None:
+        return JSONResponse({"ok": False, "code": "no_platform",
+                             "error": "平台「%s」还没有实现 session" % b.platform}, status_code=200)
+    s = pf.session(b.cookies)
     try:
         d = pf.discover(s, b.plan_id, b.project_id, b.name)
-        return {"ok": True, **d, "cookies": (pf.dump_cookies or dump_cookies)(s)}
+        return {"ok": True, **d, "cookies": (pf.dump_cookies(s) if pf.dump_cookies else [])}
     except Exception as e:
         return JSONResponse({"ok": False, "error": str(e)[:300]}, status_code=200)