chore: gitignore context-card.html (card output written in cwd)

`npx mcp-context-card card` now writes context-card.html to the working
directory by default (1.0.1). Ignore it so it can't be committed by accident.

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01Aij9ReMwQeQTVSnYUZ4Qdt

Author: Wolfe-Jam

.gitignore

@@ -6,3 +6,6 @@ project.html
 
 # npm pack artifacts
 *.tgz
+
+# card output (npx mcp-context-card card writes this in cwd)
+context-card.html