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-workspace/src/workspace_ops.rs

@@ -1604,7 +1604,7 @@ mod tests {
     /// destructuring below (no `..`) fails to compile when upstream adds or renames
     /// a field, and rebuilding `HookSpecWire` from those bindings catches wire-side
     /// drift; the assertion pins that both serde shapes stay byte-identical. The
-    /// compiled `matcher` is `#[serde(skip)]` and is the only field intentionally
+    /// compiled `matcher` is `#[serde(skip)]` and is the only field deliberately
     /// absent from the wire.
     #[test]
     fn hook_spec_wire_covers_all_upstream_fields() {