fix: handle bd --no-daemon exit code 0 bug on not-found (#339)

When bd --no-daemon show <id> does not find an issue, it incorrectly exits
with code 0 (success) but writes the error to stderr and leaves stdout empty.
This causes JSON parse failures throughout gt when code tries to unmarshal
the empty stdout.

This PR handles the bug defensively in all affected code paths:
- beads.go run(): Detect empty stdout + non-empty stderr as error
- beads.go wrapError(): Add 'no issue found' to ErrNotFound patterns
- sling.go: Check len(out) == 0 in multiple functions
- convoy.go getIssueDetails(): Check stdout.Len() == 0
- prime_molecule.go: Check stdout.Len() == 0

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

internal/cmd/convoy.go

@@ -1186,6 +1186,10 @@ func getIssueDetails(issueID string) *issueDetails {
 	if err := showCmd.Run(); err != nil {
 		return nil
 	}
+	// Handle bd --no-daemon exit 0 bug: empty stdout means not found
+	if stdout.Len() == 0 {
+		return nil
+	}
 
 	var issues []struct {
 		ID        string `json:"id"`

internal/cmd/prime_molecule.go

@@ -44,6 +44,12 @@ func showMoleculeExecutionPrompt(workDir, moleculeID string) {
 		fmt.Printf("  Check status with: bd mol current %s\n", moleculeID)
 		return
 	}
+	// Handle bd --no-daemon exit 0 bug: empty stdout means not found
+	if stdout.Len() == 0 {
+		fmt.Println(style.Bold.Render("→ PROPULSION PRINCIPLE: Work is on your hook. RUN IT."))
+		fmt.Println("  Begin working on this molecule immediately.")
+		return
+	}
 
 	// Parse JSON output - it's an array with one element
 	var outputs []MoleculeCurrentOutput

internal/cmd/sling.go

@@ -523,6 +523,10 @@ func storeArgsInBead(beadID, args string) error {
 	if err != nil {
 		return fmt.Errorf("fetching bead: %w", err)
 	}
+	// Handle bd --no-daemon exit 0 bug: empty stdout means not found
+	if len(out) == 0 {
+		return fmt.Errorf("bead not found")
+	}
 
 	// Parse the bead
 	var issues []beads.Issue
@@ -738,9 +742,15 @@ func verifyBeadExists(beadID string) error {
 	if townRoot, err := workspace.FindFromCwd(); err == nil {
 		cmd.Dir = townRoot
 	}
-	if err := cmd.Run(); err != nil {
+	// Use Output() instead of Run() to detect bd --no-daemon exit 0 bug:
+	// when issue not found, --no-daemon exits 0 but produces empty stdout.
+	out, err := cmd.Output()
+	if err != nil {
 		return fmt.Errorf("bead '%s' not found (bd show failed)", beadID)
 	}
+	if len(out) == 0 {
+		return fmt.Errorf("bead '%s' not found", beadID)
+	}
 	return nil
 }
 
@@ -764,6 +774,11 @@ func getBeadInfo(beadID string) (*beadInfo, error) {
 	if err != nil {
 		return nil, fmt.Errorf("bead '%s' not found", beadID)
 	}
+	// Handle bd --no-daemon exit 0 bug: when issue not found,
+	// --no-daemon exits 0 but produces empty stdout (error goes to stderr).
+	if len(out) == 0 {
+		return nil, fmt.Errorf("bead '%s' not found", beadID)
+	}
 	// bd show --json returns an array (issue + dependents), take first element
 	var infos []beadInfo
 	if err := json.Unmarshal(out, &infos); err != nil {
@@ -829,14 +844,16 @@ func resolveSelfTarget() (agentID string, pane string, hookRoot string, err erro
 // Uses --no-daemon with --allow-stale for consistency with verifyBeadExists.
 func verifyFormulaExists(formulaName string) error {
 	// Try bd formula show (handles all formula file formats)
+	// Use Output() instead of Run() to detect bd --no-daemon exit 0 bug:
+	// when formula not found, --no-daemon may exit 0 but produce empty stdout.
 	cmd := exec.Command("bd", "--no-daemon", "formula", "show", formulaName, "--allow-stale")
-	if err := cmd.Run(); err == nil {
+	if out, err := cmd.Output(); err == nil && len(out) > 0 {
 		return nil
 	}
 
 	// Try with mol- prefix
 	cmd = exec.Command("bd", "--no-daemon", "formula", "show", "mol-"+formulaName, "--allow-stale")
-	if err := cmd.Run(); err == nil {
+	if out, err := cmd.Output(); err == nil && len(out) > 0 {
 		return nil
 	}