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-tools/src/implementations/memory/mod.rs

@@ -10,13 +10,11 @@ pub mod types;
 pub use get_tool::MemoryGetImpl;
 pub use search_tool::MemorySearchImpl;
 
-/// Registered name of the `memory_search` tool.
-///
-/// Single source of truth shared between the tool definition and any
-/// gating callers (e.g. shell-side slash-command availability checks).
+/// Registered name of the `memory_search` tool. Single source of truth
+/// shared between the tool definition and gating callers (e.g. shell-side
+/// slash-command availability checks).
 pub const MEMORY_SEARCH_TOOL_NAME: &str = "memory_search";
 
-/// Registered name of the `memory_get` tool.
 pub const MEMORY_GET_TOOL_NAME: &str = "memory_get";
 
 #[cfg(test)]