Vendor crabrl-fork source and remove submodule linkage

- Replace `rust/crabrl-fork` gitlink with tracked source files
- Add workspace notes documenting why the fork is vendored
- Update ignore rules for vendored fork build artifacts

rust/crabrl-fork/examples/parse.rs

@@ -0,0 +1,22 @@
+//! Parse and display XBRL file info
+
+use crabrl::Parser;
+use std::env;
+
+fn main() -> Result<(), Box<dyn std::error::Error>> {
+    let args: Vec<String> = env::args().collect();
+    if args.len() != 2 {
+        eprintln!("Usage: {} <xbrl-file>", args[0]);
+        std::process::exit(1);
+    }
+
+    let parser = Parser::new();
+    let doc = parser.parse_file(&args[1])?;
+
+    println!("Parsed {}:", args[1]);
+    println!("  Facts: {}", doc.facts.len());
+    println!("  Contexts: {}", doc.contexts.len());
+    println!("  Units: {}", doc.units.len());
+
+    Ok(())
+}