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/file_tail_follower.dart

@@ -4,7 +4,7 @@
 /// process), so to "watch the same output" we open our OWN read-only follower
 /// on the file the command tails. This never spawns a process and never
 /// touches Claude's command — it just reads the file as it grows, like
-/// `tail -f`, and hands new bytes to [onData].
+/// `tail -f`, and hands new bytes to `onData`.
 ///
 /// Pure dart:io/dart:async (no Flutter) so it's unit-testable. Polls rather
 /// than using a watcher so it works uniformly across platforms and survives