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-prompt-queue/src/types.rs

@@ -11,11 +11,9 @@ pub struct QueueEntryMeta {
     pub version: u64,
     /// Enqueuing client identifier (attribution); never overwritten by edits.
     pub owner: Option<String>,
-    /// Most recent editor's client identifier, replaced on every in-place edit.
     pub last_editor: Option<String>,
     /// Display kind label; client-cosmetic kinds resolve to their send-intent before enqueue.
     pub kind: String,
-    /// Plain prompt text for the shared queue display.
     pub text: String,
 }
 
@@ -26,10 +24,8 @@ pub struct QueueEntryWire {
     pub id: String,
     #[serde(default)]
     pub version: u64,
-    /// Omitted from the wire when `None`.
     #[serde(default, skip_serializing_if = "Option::is_none")]
     pub owner: Option<String>,
-    /// Mirrors [`QueueEntryMeta::last_editor`]; omitted from the wire when `None`.
     #[serde(default, skip_serializing_if = "Option::is_none")]
     pub last_editor: Option<String>,
     #[serde(default)]
@@ -45,7 +41,6 @@ pub struct QueueEntryWire {
 #[derive(Clone, Debug, Default, Serialize, Deserialize, PartialEq, Eq)]
 #[serde(rename_all = "camelCase")]
 pub struct QueueChanged {
-    /// The session this queue belongs to; drives per-session fan-out routing.
     pub session_id: String,
     #[serde(default)]
     pub entries: Vec<QueueEntryWire>,