feat(claude): nudge fresh sessions to load the pql + clide skills (T-490)

A fresh Claude session now gets a one-line preamble (clideSkillsNote) telling it
to reach for the bundled pql + clide skills from its first turn rather than
rediscovering the workflows. Layered onto clideContextNote in the single
--append-system-prompt.

Gated on a NEW session (!spec.resume && !spec.isFork): new tabs and the
post-/clear respawn spawn with resume:false and get it; the account-change
respawn (T-480) and real resumes carry prior context (resume:true), and forks
inherit their source — none are re-nagged. Both skills already ship (pql
user-scope, clide repo-scope), so no precursor was needed.

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

test/builtin/claude/agent_bootstrap_test.dart

@@ -28,6 +28,17 @@ void main() {
     });
   });
 
+  group('clideSkillsNote (T-490)', () {
+    test('names both skills, nudges first-turn use, and stays short', () {
+      final note = clideSkillsNote();
+      expect(note, contains('`pql`'));
+      expect(note, contains('`clide`'));
+      expect(note, contains('from your first turn'));
+      // Acceptance #4: a short nudge, not a wall of text crowding clideContextNote.
+      expect(note.length, lessThan(360));
+    });
+  });
+
   group('clideBashAllowRule (T-217)', () {
     test('is the command-scoped Bash rule and rides on --allowedTools', () {
       expect(clideBashAllowRule, 'Bash(clide:*)');