Add AI artifact entries to .gitignore

Appended entries from ai_blueprint.md guidelines to exclude AI planning
files, context indexes, and assistant directories from version control:
- ai_blueprint.md and plans/
- .claude/, .gemini/, .roo/, .cline/, .cursor/, .cascade/, .windsurfrules
- *.aiindex, ai_workspace_index.json

Also untracks the already-committed .claude/ and ai_blueprint.md files.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

.gitignore

@@ -5,4 +5,28 @@ run_*/
 *.epub
 data/
 token.json
-credentials.json
+credentials.json
+
+# AI Blueprint and Context Files
+ai_blueprint.md
+plans/
+
+# Claude / Anthropic Artifacts
+.claude/
+claude.json
+
+# Gemini / Google Artifacts
+.gemini/
+gemini_history.json
+
+# AI Coding Assistant Directories (Roo Code, Cline, Cursor, Windsurf)
+.roo/
+.cline/
+.cursor/
+.cursorrules
+.windsurfrules
+.cascade/
+
+# AI Generated Index and Memory Cache Files
+*.aiindex
+ai_workspace_index.json