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/up.go

@@ -200,11 +200,11 @@ func ensureSession(t *tmux.Tmux, sessionName, workDir, role string) error {
 		return err
 	}
 
-	// Set environment
+	// Set environment (non-fatal: session works without these)
 	_ = t.SetEnvironment(sessionName, "GT_ROLE", role)
 	_ = t.SetEnvironment(sessionName, "BD_ACTOR", role)
 
-	// Apply theme based on role
+	// Apply theme based on role (non-fatal: theming failure doesn't affect operation)
 	switch role {
 	case "mayor":
 		theme := tmux.MayorTheme()
@@ -246,13 +246,13 @@ func ensureWitness(t *tmux.Tmux, sessionName, rigPath, rigName string) error {
 		return err
 	}
 
-	// Set environment
+	// Set environment (non-fatal: session works without these)
 	bdActor := fmt.Sprintf("%s/witness", rigName)
 	_ = t.SetEnvironment(sessionName, "GT_ROLE", "witness")
 	_ = t.SetEnvironment(sessionName, "GT_RIG", rigName)
 	_ = t.SetEnvironment(sessionName, "BD_ACTOR", bdActor)
 
-	// Apply theme (use rig-based theme)
+	// Apply theme (non-fatal: theming failure doesn't affect operation)
 	theme := tmux.AssignTheme(rigName)
 	_ = t.ConfigureGasTownSession(sessionName, theme, "", "Witness", rigName)