To avoid permission denied errors when modifying Tailscale configuration (serve/funnel),
we now attempt the command directly first. If it fails, we catch the error and retry
with `sudo -n`. This preserves existing behavior for users where it works, but
attempts to escalate privileges (non-interactively) if needed.
- Added `execWithSudoFallback` helper in `src/infra/tailscale.ts`.
- Updated `ensureFunnel`, `enableTailscaleServe`, `disableTailscaleServe`,
`enableTailscaleFunnel`, and `disableTailscaleFunnel` to use the fallback helper.
- Added tests in `src/infra/tailscale.test.ts` to verify fallback behavior.