Document intentional error suppressions with comments (gt-zn9m)

All 156 instances of _ = error suppression in non-test code now have
explanatory comments documenting why the error is intentionally ignored.

Categories of intentional suppressions:
- non-fatal: session works without these - tmux environment setup
- non-fatal: theming failure does not affect operation - visual styling
- best-effort cleanup - defer cleanup on failure paths
- best-effort notification - mail/notifications that should not block
- best-effort interrupt - graceful shutdown attempts
- crypto/rand.Read only fails on broken system - random ID generation
- output errors non-actionable - fmt.Fprint to io.Writer

This addresses the silent failure and debugging concerns raised in the
issue by making the intentionality explicit in the code.

Generated with Claude Code https://claude.com/claude-code

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

internal/cmd/molecule_list.go

@@ -166,7 +166,7 @@ func runMoleculeShow(cmd *cobra.Command, args []string) error {
 
 	// Parse steps
 	steps, parseErr := beads.ParseMoleculeSteps(mol.Description)
-	_ = source // Used below in output
+	_ = source // silence unused warning; used in output formatting below
 
 	// For JSON, include parsed steps
 	if moleculeJSON {