feat: implement Step.Condition evaluation in bd cook (bd-7zka.1)

Add compile-time step filtering based on formula variables:
- New EvaluateStepCondition function for {{var}} truthy and equality checks
- FilterStepsByCondition to exclude steps based on conditions
- Integration into pour, wisp, and mol bond commands
- Supports: {{var}}, {{var}} == value, {{var}} != value

Steps with conditions that evaluate to false are excluded from the
cooked formula, along with their children.

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

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

cmd/bd/wisp.go

@@ -167,7 +167,8 @@ func runWispCreate(cmd *cobra.Command, args []string) {
 
 	// Try to cook formula inline (ephemeral protos)
 	// This works for any valid formula name, not just "mol-" prefixed ones
-	sg, err := resolveAndCookFormula(args[0], nil)
+	// Pass vars for step condition filtering (bd-7zka.1)
+	sg, err := resolveAndCookFormulaWithVars(args[0], nil, vars)
 	if err == nil {
 		subgraph = sg
 		protoID = sg.Root.ID