fix(version): replace hardcoded v3.0.0 with dynamic _skill_version()

render.py, ui.py, and last30days.py had hardcoded "v3.0.0" in titles
and headers while plugin.json was at 3.1.1. Use _skill_version()
(reads from plugin.json at runtime) so version strings stay in sync.

Fixes #284

skills/last30days/scripts/lib/render.py

@@ -96,7 +96,7 @@ def render_compact(report: schema.Report, cluster_limit: int = 8, fun_level: str
     non_empty = [s for s, items in sorted(report.items_by_source.items()) if items]
     lines = [
         *_render_badge(),
-        f"# last30days v3.0.0: {report.topic}",
+        f"# last30days v{_skill_version()}: {report.topic}",
         "",
         *_assistant_safety_lines(),
         f"- Date range: {report.range_from} to {report.range_to}",
@@ -602,7 +602,7 @@ def render_comparison_multi(
 
     lines: list[str] = [
         *_render_badge(),
-        f"# last30days v3.0.0: {synthesized_topic}",
+        f"# last30days v{_skill_version()}: {synthesized_topic}",
         "",
         *_assistant_safety_lines(),
         f"- Comparison mode: {len(entities)} entities ({', '.join(entities)})",
@@ -790,7 +790,7 @@ def render_full(report: schema.Report) -> str:
     # Start with the same header as compact
     non_empty = [s for s, items in sorted(report.items_by_source.items()) if items]
     lines = [
-        f"# last30days v3.0.0: {report.topic}",
+        f"# last30days v{_skill_version()}: {report.topic}",
         "",
         *_assistant_safety_lines(),
         f"- Date range: {report.range_from} to {report.range_to}",