fix: Resolve build errors and warnings, and update grammar

Co-authored-by: aider (openai/andrew/openrouter/sonoma-sky-alpha) <aider@aider.chat>

src/parser/filter.pest

@@ -1,6 +1,6 @@
 WHITESPACE = _{ " " | "\t" | "\n" | "\r" }
 
-#! This Pest grammar defines the syntax for filter chains used in the Keep application.
+//! This Pest grammar defines the syntax for filter chains used in the Keep application.
 
 // Main entry point for parsing multiple filters separated by pipes
 filters = { SOI ~ filter ~ (pipe ~ filter)* ~ EOI }