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/send/contributors/turn_lifecycle.rs

@@ -1,6 +1,5 @@
 use async_trait::async_trait;
 
-/// Input supplied when the host starts a turn.
 pub struct TurnStartInput {
     /// True when the harness produced the turn (auto-wake, drain, cron, continuation), not the user.
     pub synthetic: bool,
@@ -12,19 +11,16 @@ impl TurnStartInput {
     }
 }
 
-/// Input supplied when the host completes a turn.
 pub struct TurnDoneInput;
 
-/// Why the host aborted the turn instead of completing it.
 #[derive(Clone, Copy, Debug, PartialEq, Eq)]
 pub enum TurnAbortReason {
     /// The client went away mid-turn.
     Disconnected,
-    /// The user interrupted the turn before it completed.
+    /// The user cancelled mid-turn.
     Interrupted,
 }
 
-/// Input supplied when the host aborts a turn.
 pub struct TurnAbortInput {
     pub reason: TurnAbortReason,
 }
@@ -35,7 +31,6 @@ impl TurnAbortInput {
     }
 }
 
-/// Input supplied when the host observes an error for a turn.
 pub struct TurnErrorInput<'a> {
     pub message: &'a str,
 }