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-acp-lib/src/message.rs

@@ -26,16 +26,20 @@ pub trait AcpSide {
 
 /// Marker type representing the agent's view of the ACP connection (as one side of that connection).
 impl AcpSide for acp::AgentSide {
-    type InMessage = AcpAgentMessage; // inbound messages = messages meant *for* the agent
-    type OutMessage = AcpClientMessage; // outbound messages = messages meant *for* the client
+    // inbound messages = messages meant *for* the agent
+    type InMessage = AcpAgentMessage;
+    // outbound messages = messages meant *for* the client
+    type OutMessage = AcpClientMessage;
     type OtherSide = acp::ClientSide;
     const NAME: &'static str = "agent";
 }
 
 /// Marker type representing the agent's view of the ACP connection (as one side of that connection).
 impl AcpSide for acp::ClientSide {
-    type InMessage = AcpClientMessage; // inbound messages = messages meant *for* the client
-    type OutMessage = AcpAgentMessage; // outbound messages = messages meant *for* the agent
+    // inbound messages = messages meant *for* the client
+    type InMessage = AcpClientMessage;
+    // outbound messages = messages meant *for* the agent
+    type OutMessage = AcpAgentMessage;
     type OtherSide = acp::AgentSide;
     const NAME: &'static str = "client";
 }
@@ -241,7 +245,8 @@ mod client {
 
         pub fn route_to_client(
             self,
-            client: impl acp::Client + 'static, // note: acp::Client is auto-implemented for Rc/Arc
+            // note: acp::Client is auto-implemented for Rc/Arc
+            client: impl acp::Client + 'static,
             spawn: impl Fn(LocalBoxFuture<'static, ()>) + 'static,
         ) {
             match self {
@@ -540,7 +545,8 @@ mod agent {
 
         pub fn route_to_agent(
             self,
-            agent: impl acp::Agent + 'static, // note: acp::Agent is auto-implemented for Rc/Arc
+            // note: acp::Agent is auto-implemented for Rc/Arc
+            agent: impl acp::Agent + 'static,
             spawn: impl Fn(LocalBoxFuture<'static, ()>) + 'static,
         ) {
             match self {