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-system-power/src/macos.rs

@@ -46,8 +46,10 @@ type IoServiceInterestCallback = extern "C" fn(
 
 #[link(name = "CoreFoundation", kind = "framework")]
 unsafe extern "C" {
-    static kCFRunLoopCommonModes: *const c_void; // CFRunLoopMode (CFStringRef)
-    static kCFRunLoopDefaultMode: *const c_void; // CFRunLoopMode (CFStringRef)
+    // CFRunLoopMode (CFStringRef)
+    static kCFRunLoopCommonModes: *const c_void;
+    // CFRunLoopMode (CFStringRef)
+    static kCFRunLoopDefaultMode: *const c_void;
     fn CFRunLoopGetCurrent() -> *mut c_void;
     fn CFRunLoopRunInMode(
         mode: *const c_void,
@@ -274,7 +276,7 @@ extern "C" fn power_callback(
     if let Some(event) = event {
         // For sleep-bound messages the ack is sent only *after* the callback
         // returns: a `WillSleep` handler may block (bounded) waiting for an
-        // in-flight token refresh to finish, which intentionally delays the
+        // in-flight token refresh to finish, which deliberately delays the
         // `IOAllowPowerChange` and holds off the suspend. IOKit allows ~30 s
         // per phase before forcing sleep, so a bounded wait is safe. See the
         // `kigi_system_power` crate-level callback contract.