docs: fix 41 unresolved dartdoc references

Convert non-resolving [refs] in doc comments to backtick code-spans across 24
lib/ files (param/field names out of doc scope, method refs on other classes,
non-API strings like regex char-classes and command ids). Verified 0
"unresolved doc reference" warnings via `dart doc --validate-links`. The
dart-doc CI gate (test.yml) never ran before — Gitea Actions was inactive — so
this debt had accumulated unchecked.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

lib/kernel/src/keymap/when_clause.dart

@@ -6,7 +6,7 @@
 ///   and   := unary ('&&' unary)*
 ///   unary := '!' unary | atom
 ///   atom  := IDENT | '(' expr ')'
-///   IDENT := [a-zA-Z_][a-zA-Z0-9._-]*
+///   IDENT := `[a-zA-Z_][a-zA-Z0-9._-]*`
 ///
 /// Identifiers resolve against a `Map<String, bool>` context. A missing
 /// identifier evaluates to `false` — bindings can assume any required