chore: strip remaining pre-fork version references

Second pass — removes chat-switchboard version numbers from config
field docs, section headers, file headers, and test comments. These
were pre-fork version tags that don't apply to switchboard-core.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

server/handlers/workflow_signoff_handlers.go

@@ -10,7 +10,7 @@ import (
 	"switchboard-core/workflow"
 )
 
-// ── Signoff Handlers (v0.3.4) ─────────────────
+// ── Signoff Handlers ─────────────────
 
 // WorkflowSignoffHandler manages signoff HTTP endpoints.
 type WorkflowSignoffHandler struct {