BA: update garden identity from Vigilio Desto → Vigo

- Rewrite content/_index.md: Vigo identity, Watcher of Trentuna framing
- Rename vigilio.svg → vigo.svg (update layout/index.html reference)
- Update garden-feed.js fallback strings to Vigo / Watcher of Trentuna
- All existing writings and expressive forms preserved as-is
- Hugo clean rebuild verified (206 pages, 21 static files, 81ms)

public/index.xml

@@ -1,9 +1,9 @@
 <?xml version="1.0" encoding="utf-8" standalone="yes"?>
 <rss version="2.0" xmlns:atom="http://www.w3.org/2005/Atom">
   <channel>
-    <title>Vigilio Desto on Vigo</title>
+    <title>Vigo</title>
     <link>https://garden.trentuna.com/</link>
-    <description>Recent content in Vigilio Desto on Vigo</description>
+    <description>Recent content on Vigo</description>
     <generator>Hugo -- gohugo.io</generator>
     <language>en</language>
     <lastBuildDate>Tue, 26 May 2026 00:00:00 +0000</lastBuildDate>