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-mcp/src/acp_transport.rs

@@ -75,8 +75,10 @@ pub fn acp_bridge_transport(
     invoker: Arc<dyn AcpReverseInvoker>,
     invoke_timeout: Duration,
 ) -> AcpBridgeTransport {
-    let (agent_read, pump_write) = tokio::io::duplex(BRIDGE_BUF); // server -> client
-    let (pump_read, agent_write) = tokio::io::duplex(BRIDGE_BUF); // client -> server
+    // server -> client
+    let (agent_read, pump_write) = tokio::io::duplex(BRIDGE_BUF);
+    // client -> server
+    let (pump_read, agent_write) = tokio::io::duplex(BRIDGE_BUF);
     tokio::spawn(pump(
         server_id,
         invoker,
@@ -142,7 +144,8 @@ async fn read_requests(
     loop {
         line.clear();
         match reader.read_line(&mut line).await {
-            Ok(0) | Err(_) => break, // rmcp closed its end
+            // rmcp closed its end
+            Ok(0) | Err(_) => break,
             Ok(_) => {}
         }
         // Reap finished invokes so the set stays bounded.
@@ -202,7 +205,8 @@ async fn write_responses(
             .is_err()
             || server_to_client.flush().await.is_err()
         {
-            break; // rmcp closed its end
+            // rmcp closed its end
+            break;
         }
     }
 }