v0.6.3: easier install, clearer status

• The one-line installers on pilot start pages no longer depend on pipx. If Python 3.10+ is there, Squidbrake gets its own virtual environment; if not (macOS ships 3.9), uv installs it with a Python of its own. Any failure ends with a clear message saying what to do.
• squidbrake connect status checks the dashboard your agents' hooks actually use (a hosted one too) and says plainly when their key is rejected, instead of suggesting you start a local gateway.