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/beads/molecule.go

@@ -247,7 +247,7 @@ func (b *Beads) instantiateFromChildren(mol *Issue, parent *Issue, templates []*
 
 		child, err := b.Create(childOpts)
 		if err != nil {
-			// Attempt to clean up created issues on failure
+			// Attempt to clean up created issues on failure (best-effort cleanup)
 			for _, created := range createdIssues {
 				_ = b.Close(created.ID)
 			}
@@ -340,7 +340,7 @@ func (b *Beads) instantiateFromMarkdown(mol *Issue, parent *Issue, opts Instanti
 
 		child, err := b.Create(childOpts)
 		if err != nil {
-			// Attempt to clean up created issues on failure
+			// Attempt to clean up created issues on failure (best-effort cleanup)
 			for _, created := range createdIssues {
 				_ = b.Close(created.ID)
 			}