docs(comments): rewrite comments across all crates to the guidelines

Sweep every first-party crate source (1956 .rs files) to the project comment
guidelines: delete redundant restatements, decorative banners, change
narration, and end-of-line comments; keep and tighten the crucial ones
(invariants, bug rationale, SAFETY blocks, ported-source attribution).

No functional code changed. Every edit is proven comment-only against the
prior tree by a comment-stripping lexer (string/char/raw-string aware) plus a
separate doctest-fence check. Where removing a comment made rustfmt or clippy
want to re-lay-out adjacent code, the minimal triggering comment is restored so
code tokens stay byte-identical.

Gates green: cargo fmt --all --check (0 diffs), cargo check and cargo clippy
--workspace --all-targets (0 warnings).

Adds scripts/check_codegen_comment_guidelines.py — the enforcement gate for
these guidelines (flags banners, end-of-line comments, change narration, and
commented-out code).

crates/codegen/kigi-agent-lifecycle/src/local/contributors/command.rs

@@ -4,8 +4,9 @@ use crate::send::contributors::command::{
     CommandAction, CommandContributor, CommandInvocation, CommandSpec,
 };
 
-/// `?Send` twin of [`CommandContributor`] for single-threaded hosts like kigi build's TUI agent, whose session state is `Rc`/`RefCell`-based and can
-/// never satisfy the `Send` bounds the send flavor bakes into its boxed hook futures.
+/// `?Send` twin of [`CommandContributor`] for single-threaded hosts like kigi build's TUI agent,
+/// whose session state is `Rc`/`RefCell`-based and can never satisfy the `Send` bounds the send
+/// flavor bakes into its boxed hook futures.
 #[async_trait(?Send)]
 pub trait LocalCommandContributor {
     fn advertised_commands(&self) -> Vec<CommandSpec>;
@@ -14,7 +15,8 @@ pub trait LocalCommandContributor {
     -> Result<CommandAction, String>;
 }
 
-/// Send contributors work in single-threaded hosts as-is, so shared logic implements [`CommandContributor`] once and both hosts can register it.
+/// Send contributors work in single-threaded hosts as-is, so shared logic implements
+/// [`CommandContributor`] once and both hosts can register it.
 #[async_trait(?Send)]
 impl<T: CommandContributor> LocalCommandContributor for T {
     fn advertised_commands(&self) -> Vec<CommandSpec> {