fix(lsp): display diagnostics errors as error blocks in TUI

- Changed lsp_diagnostics error handling to throw errors instead of returning strings
- Line 211: Changed from `return output` to `throw new Error(output)`
- Makes errors display as proper error blocks in TUI

Co-authored-by: Sisyphus <clio-agent@sisyphuslabs.ai>

src/tools/lsp/tools.ts

@@ -208,7 +208,7 @@ export const lsp_diagnostics: ToolDefinition = tool({
       return output
     } catch (e) {
       const output = `Error: ${e instanceof Error ? e.message : String(e)}`
-      return output
+      throw new Error(output)
     }
   },
 })