fix: security, correctness, and test hardening from review

- routes.py: reject glob wildcards (* ? [ ]) in skill name param to
  prevent rglob wildcard injection when serving linked files
- panels.js: replace inline onclick+esc() with data-* attributes and
  addEventListener for skill tag removal and linked-file clicks;
  esc() is HTML-safe but not JS-safe -- apostrophes in names caused
  JS syntax errors and _cronSelectedSkills array corruption
- ui.js: fix _fmtTokens(null/undefined) returning 'null'/'undefined'
  by guarding with (!n||n<0) -> '0'; add data-role attribute to msg-row
  elements so usage badge correctly targets the last assistant row
  instead of the last row regardless of speaker
- tests: rename test_sprint24.py -> test_sprint23.py (wrong sprint #);
  add 3 new tests: path traversal rejection, wildcard name rejection,
  cron create with skills; strengthen existing tests to assert field
  presence explicitly (was using .get(field, 0)==0 which never caught
  a missing field)

api/routes.py

@@ -230,6 +230,9 @@ def handle_get(handler, parsed):
         file_path = qs.get('file', [''])[0]
         if file_path:
             # Serve a linked file from the skill directory
+            import re as _re
+            if _re.search(r'[*?\[\]]', name):
+                return bad(handler, 'Invalid skill name', 400)
             skill_dir = None
             for p in SKILLS_DIR.rglob(name):
                 if p.is_dir(): skill_dir = p; break