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/foreign_sessions/capability/mod.rs

@@ -259,7 +259,7 @@ fn open_sqlite_transaction_with_journal_mode(
     // non-symlink final file are validated above; adversarial swap-and-restore
     // races are outside this scanner's local-user threat model. Only local WAL
     // reaches this direct read-only/query-only open; its native coordination may
-    // still update SHM read marks despite scanner SQL making no logical writes.
+    // still touch SHM read marks despite scanner SQL making no logical writes.
     let connection = Connection::open_with_flags(
         &opened.path,
         OpenFlags::SQLITE_OPEN_READ_ONLY

crates/codegen/kigi-workspace/src/foreign_sessions/claude.rs

@@ -485,6 +485,8 @@ fn is_generated_prompt(value: &str) -> bool {
         return true;
     }
     let value = value.trim_start();
+    // Tool-injected wrappers open with a lowercase tag (`<command-message>`,
+    // `<local-command-stdout>`); prose a user types rarely does.
     value
         .strip_prefix('<')
         .and_then(|rest| rest.chars().next())

crates/codegen/kigi-workspace/src/foreign_sessions/claude/projects.rs

@@ -9,6 +9,8 @@ pub(super) fn scoped_project_dirs(config_dir: &Path, cwd: &Path) -> Vec<PathBuf>
     if let Ok(repository) = git2::Repository::discover(cwd) {
         if let Some(workdir) = repository.workdir() {
             paths.push(dunce::canonicalize(workdir).unwrap_or_else(|_| workdir.to_path_buf()));
+            // A linked worktree has its own gitdir distinct from the shared
+            // commondir, whose parent is the main worktree.
             if repository.path() != repository.commondir()
                 && let Some(main_workdir) = repository.commondir().parent()
             {

crates/codegen/kigi-workspace/src/foreign_sessions/codex/mod.rs

@@ -78,6 +78,8 @@ fn highest_named_state_database(root: &ApprovedRoot) -> Option<PathBuf> {
         match std::fs::symlink_metadata(&path) {
             Ok(_) => Some(path),
             Err(error) if error.kind() == std::io::ErrorKind::NotFound => None,
+            // An unreadable entry still claims its generation, so the caller
+            // falls back to rollout files instead of trusting an older database.
             Err(_) => Some(path),
         }
     })

crates/codegen/kigi-workspace/src/foreign_sessions/mod.rs

@@ -1,7 +1,7 @@
 //! Bounded, metadata-only listing of foreign coding-agent sessions.
 //! Foreign SQLite stores are opened only when `kigi_sqlite_journal::JournalMode`
 //! selects local WAL. The direct read-only/query-only transaction makes no
-//! logical writes, though WAL coordination may update shared-memory read marks.
+//! logical writes, though WAL coordination may touch shared-memory read marks.
 //! Network filesystems fail soft before SQLite open, conversion, or writes.
 use std::cmp::Ordering;
 use std::collections::HashSet;