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/transcript_reader.dart

@@ -24,7 +24,7 @@
 ///
 /// # Version drift-guard
 /// If the envelope `version` field has an unfamiliar major version the reader
-/// warns via [onWarn] (or stderr if omitted) and degrades gracefully — it
+/// warns via `onWarn` (or stderr if omitted) and degrades gracefully — it
 /// parses whatever it can and skips the rest rather than crashing.
 library;
 
@@ -227,7 +227,7 @@ class TranscriptReader {
   /// [pollInterval] controls how often the reader polls for new data and
   /// session switches (default 500 ms).
   ///
-  /// [onWarn] receives warning messages from the version drift-guard.
+  /// `onWarn` receives warning messages from the version drift-guard.
   /// If omitted, warnings are written to stderr.
   TranscriptReader(
     this.workspacePath, {
@@ -419,7 +419,7 @@ class TranscriptReader {
   }
 
   /// Parse a single JSONL line into its items (forwarding any version
-  /// warnings to [onWarn]). Public so tests exercise the real parser.
+  /// warnings to `onWarn`). Public so tests exercise the real parser.
   List<ConversationItem> parseLine(String line) {
     final parsed = parseTranscriptChunk(line);
     for (final w in parsed.warnings) {