Add single-instance support and clean up scaffolding files

Ensure only one Vesper instance runs at a time. When a second
instance is launched with a file argument, the file is forwarded
to the existing window. Remove unused template SVGs and test file.

.gitignore

@@ -23,8 +23,7 @@ nul
 data/
 
 # Editor directories and files
-.vscode/*
-!.vscode/extensions.json
+.vscode/
 .idea
 .DS_Store
 *.suo
@@ -32,3 +31,21 @@ data/
 *.njsproj
 *.sln
 *.sw?
+
+# AI/LLM tooling
+.claude/
+.cursor/
+.copilot/
+.codeium/
+.tabnine/
+.aider*
+.continue/
+
+# Trash
+trash/
+
+# Docs
+docs/
+
+# This file
+.gitignore