fix: support empty string literals in textfx

- Fix tokenizer to emit empty string token when closing quote on empty buffer
- Add force parameter to flush_word() to handle empty quoted strings
- Add test case for echo "" and echo ''

konabot/plugins/handle_text/base.py

@@ -161,9 +161,9 @@ class PipelineRunner:
             "'": "'",
         }
 
-        def flush_word():
+        def flush_word(force: bool = False):
             nonlocal buf
-            if buf:
+            if buf or force:
                 tokens.append(Token(TokenKind.WORD, buf))
                 buf = ""
 
@@ -178,6 +178,7 @@ class PipelineRunner:
                     escape = True
                 elif c == quote:
                     quote = None
+                    flush_word(force=True)  # 引号闭合时强制 flush，即使是空字符串
                 else:
                     buf += c
                 i += 1
@@ -188,7 +189,7 @@ class PipelineRunner:
                 i += 1
                 continue
 
-            if c.isspace() or c in "  ":
+            if c.isspace() or c in "  ":
                 flush_word()
                 i += 1
                 continue