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/builtin/claude/src/team_chat_model.dart

@@ -5,8 +5,8 @@
 /// and the full workspace pane read from this one model — they share state,
 /// they do NOT each hold their own copy.
 ///
-/// [postAsUser] is the user's write path: it routes by @tag (one agent or
-/// broadcast) and, when the interrupt flag is set, calls [interrupt()] on the
+/// `postAsUser` is the user's write path: it routes by @tag (one agent or
+/// broadcast) and, when the interrupt flag is set, calls `interrupt()` on the
 /// target session THEN delivers the message.
 ///
 /// Flutter-free on purpose: this module (like [TeamBroker]) runs under