Add Aider integration for beads issue tracking

Implements GH#206 and bd-3djj: Add support for Aider AI pair programming
tool with beads issue tracking.

Changes:
- Added cmd/bd/setup/aider.go with InstallAider, CheckAider, RemoveAider
- Created .aider.conf.yml template with bd workflow instructions
- Added .aider/README.md template with quick reference
- Updated cmd/bd/setup.go to include aider subcommand
- Fixed cmd/bd/main.go to allow setup subcommands without database by
  checking parent command name
- Added comprehensive docs/AIDER_INTEGRATION.md documentation

Key differences from Claude/Cursor integration:
- Aider requires explicit command execution via /run
- AI suggests bd commands rather than running autonomously
- Documentation emphasizes human-in-the-loop workflow
- Config instructs AI to always suggest, never execute

Usage:
  bd setup aider          # Install integration
  bd setup aider --check  # Verify installation
  bd setup aider --remove # Remove integration

Resolves bd-3djj
Related to GH#206

🤖 Generated with [Claude Code](https://claude.com/claude-code)

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

cmd/bd/setup.go

@@ -14,7 +14,7 @@ var (
 var setupCmd = &cobra.Command{
 	Use:   "setup",
 	Short: "Setup integration with AI editors",
-	Long:  `Setup integration files for AI editors like Claude Code and Cursor.`,
+	Long:  `Setup integration files for AI editors like Claude Code, Cursor, and Aider.`,
 }
 
 var setupCursorCmd = &cobra.Command{
@@ -39,6 +39,32 @@ Uses BEGIN/END markers for safe idempotent updates.`,
 	},
 }
 
+var setupAiderCmd = &cobra.Command{
+	Use:   "aider",
+	Short: "Setup Aider integration",
+	Long: `Install Beads workflow configuration for Aider.
+
+Creates .aider.conf.yml with bd workflow instructions.
+The AI will suggest bd commands for you to run via /run.
+
+Note: Aider requires explicit command execution - the AI cannot
+run commands autonomously. It will suggest bd commands which you
+must confirm using Aider's /run command.`,
+	Run: func(cmd *cobra.Command, args []string) {
+		if setupCheck {
+			setup.CheckAider()
+			return
+		}
+
+		if setupRemove {
+			setup.RemoveAider()
+			return
+		}
+
+		setup.InstallAider()
+	},
+}
+
 var setupClaudeCmd = &cobra.Command{
 	Use:   "claude",
 	Short: "Setup Claude Code integration",
@@ -72,7 +98,11 @@ func init() {
 	setupCursorCmd.Flags().BoolVar(&setupCheck, "check", false, "Check if Cursor integration is installed")
 	setupCursorCmd.Flags().BoolVar(&setupRemove, "remove", false, "Remove bd rules from Cursor")
 
+	setupAiderCmd.Flags().BoolVar(&setupCheck, "check", false, "Check if Aider integration is installed")
+	setupAiderCmd.Flags().BoolVar(&setupRemove, "remove", false, "Remove bd config from Aider")
+
 	setupCmd.AddCommand(setupClaudeCmd)
 	setupCmd.AddCommand(setupCursorCmd)
+	setupCmd.AddCommand(setupAiderCmd)
 	rootCmd.AddCommand(setupCmd)
 }