feat(cli): merge chat into default behavior, default cwd to workspace/

- Remove standalone chat subcommand; chat becomes default behavior
- Default --cwd resolves to workspace/ instead of repo root
- Split CLAUDE.md: repo/ for CLI dev, workspace/ for daily workflow
- Add workspace/CLAUDE.md, workspace/.gitignore for tmp files
- Ignore MCP temp artifacts (.mcp.json, .playwright-mcp/)
- Clean up removed mail subcommand files

.gitignore

@@ -9,3 +9,12 @@ knowledge/
 
 .claude/
 .obsidian/
+
+# MCP configs and temp artifacts
+.mcp.json
+.playwright-mcp/
+
+# Playwright MCP default screenshots — always use workspace/tmp/ instead
+/*.png
+/*.jpg
+/*.jpeg