refactor: Apply tech debt remediation from stashed changes

- Update tokio from 1.48 to 1.49 for latest async runtime improvements
- Rewrite state_bench.rs to use std::hint::black_box (Rust 1.66+)
  instead of criterion::black_box for better optimization barriers
- Update parser_bench.rs to use std::hint::black_box consistently
- Apply clippy fixes to rustirc-scripting and rustirc-plugins crates
- Enhance documentation in ScriptApi with detailed field comments
- Improve plugins manager code organization

Co-Authored-By: Claude Opus 4.5 <[email protected]>

Author: doublegate

Cargo.lock

@@ -16,7 +16,7 @@ rustdoc-args = ["--cfg", "docsrs"]
 
 [workspace.dependencies]
 # Async runtime
-tokio = { version = "1.48", features = ["full"] }
+tokio = { version = "1.49", features = ["full"] }
 tokio-rustls = "0.26"
 
 # TLS