Handle unknown lexer, remove dead _THEMES list, tighten JSON detection - Catch unknown Pygments lexer names and fall back to plain text - Remove unused _THEMES list from cli.py - Only auto-detect JSON when content starts with { or [ to avoid false positives on trivial values like strings or numbers

src/rp/render.py

@@ -44,9 +44,14 @@ def render(
                 content, "json", theme=options.theme, line_numbers=line_numbers
             )
     else:
-        renderable = Syntax(
-            content, file_type, theme=options.theme, line_numbers=line_numbers
-        )
+        try:
+            renderable = Syntax(
+                content, file_type, theme=options.theme, line_numbers=line_numbers
+            )
+        except Exception:
+            renderable = Syntax(
+                content, "text", theme=options.theme, line_numbers=line_numbers
+            )
 
     if use_pager:
         with console.pager(styles=True):