feat(deps): Auto-install beads (bd) when missing (GHI #22)

- Add internal/deps package for dependency management
- Check for bd before gt install and gt rig add
- Auto-install bd via go install if missing
- Version check warns if bd is too old (min: 0.43.0)

Closes #22

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

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

internal/cmd/install.go

@@ -11,6 +11,7 @@ import (
 
 	"github.com/spf13/cobra"
 	"github.com/steveyegge/gastown/internal/config"
+	"github.com/steveyegge/gastown/internal/deps"
 	"github.com/steveyegge/gastown/internal/style"
 	"github.com/steveyegge/gastown/internal/templates"
 	"github.com/steveyegge/gastown/internal/workspace"
@@ -105,6 +106,13 @@ func runInstall(cmd *cobra.Command, args []string) error {
 		style.PrintWarning("Creating HQ inside existing workspace at %s", existingRoot)
 	}
 
+	// Ensure beads (bd) is available before proceeding
+	if !installNoBeads {
+		if err := deps.EnsureBeads(true); err != nil {
+			return fmt.Errorf("beads dependency check failed: %w", err)
+		}
+	}
+
 	fmt.Printf("%s Creating Gas Town HQ at %s\n\n",
 		style.Bold.Render("🏭"), style.Dim.Render(absPath))
 

internal/cmd/rig.go

@@ -11,6 +11,7 @@ import (
 	"github.com/spf13/cobra"
 	"github.com/steveyegge/gastown/internal/beads"
 	"github.com/steveyegge/gastown/internal/config"
+	"github.com/steveyegge/gastown/internal/deps"
 	"github.com/steveyegge/gastown/internal/git"
 	"github.com/steveyegge/gastown/internal/polecat"
 	"github.com/steveyegge/gastown/internal/refinery"
@@ -193,6 +194,11 @@ func runRigAdd(cmd *cobra.Command, args []string) error {
 	name := args[0]
 	gitURL := args[1]
 
+	// Ensure beads (bd) is available before proceeding
+	if err := deps.EnsureBeads(true); err != nil {
+		return fmt.Errorf("beads dependency check failed: %w", err)
+	}
+
 	// Find workspace
 	townRoot, err := workspace.FindFromCwdOrError()
 	if err != nil {