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/crew_lifecycle.go

@@ -135,7 +135,7 @@ func runCrewRefresh(cmd *cobra.Command, args []string) error {
 		return fmt.Errorf("creating session: %w", err)
 	}
 
-	// Set environment
+	// Set environment (non-fatal: session works without these)
 	_ = t.SetEnvironment(sessionID, "GT_RIG", r.Name)
 	_ = t.SetEnvironment(sessionID, "GT_CREW", name)
 
@@ -224,7 +224,7 @@ func runCrewRestart(cmd *cobra.Command, args []string) error {
 	t.SetEnvironment(sessionID, "GT_RIG", r.Name)
 	t.SetEnvironment(sessionID, "GT_CREW", name)
 
-	// Apply rig-based theming (uses config if set, falls back to hash)
+	// Apply rig-based theming (non-fatal: theming failure doesn't affect operation)
 	theme := getThemeForRig(r.Name)
 	_ = t.ConfigureGasTownSession(sessionID, theme, r.Name, name, "crew")