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-sandbox/src/logging.rs

@@ -1,15 +1,13 @@
 //! Sandbox event logger.
 //!
-//! Records sandbox events (profile applied, violations, bypasses) for
-//! telemetry and debugging. Events are kept in memory and can be flushed
-//! to a JSONL file at `~/.kigi/sandbox-events.jsonl`.
+//! Events (profile applied, violations, bypasses) are buffered in memory and
+//! flushed as JSONL to `~/.kigi/sandbox-events.jsonl`.
 
 use std::path::PathBuf;
 use std::sync::Mutex;
 
 use crate::types::{SandboxEvent, SandboxEventType, SandboxMetrics};
 
-/// Logger that collects sandbox events and maintains violation counters.
 pub struct SandboxLogger {
     events: Mutex<Vec<SandboxEvent>>,
     metrics: SandboxMetrics,
@@ -23,7 +21,6 @@ impl SandboxLogger {
         }
     }
 
-    /// Record an event, updating metrics counters as appropriate.
     pub fn log(&self, event: SandboxEvent) {
         match &event.event_type {
             SandboxEventType::FsViolation => self.metrics.inc_fs_violation(),
@@ -46,12 +43,11 @@ impl SandboxLogger {
         }
     }
 
-    /// Get a reference to the metrics counters.
     pub fn metrics(&self) -> &SandboxMetrics {
         &self.metrics
     }
 
-    /// Take all accumulated events, draining the internal buffer.
+    /// Drains the buffer.
     pub fn take_events(&self) -> Vec<SandboxEvent> {
         self.events
             .lock()
@@ -59,8 +55,6 @@ impl SandboxLogger {
             .unwrap_or_default()
     }
 
-    /// Flush accumulated events to the JSONL log file.
-    /// Each event is written as a single JSON line.
     pub fn flush_to_disk(&self) -> anyhow::Result<()> {
         let events = self.take_events();
         if events.is_empty() {