fix(v2ray): race-free config cleanup, replace fixed 2s setTimeout

[Sentinel-Bluebuilder]

Summary

The V2Ray config at <tmpdir>/sentinel-v2ray/config.json contains the per-session UUID and was being deleted by a fixed setTimeout(..., 2000) right after spawn(). Two problems with that:

1. Race against the next loop iteration. cfgPath is the same path every attempt (config.json, not unique-per-attempt). If outbound A's V2Ray dies fast and the loop iterates to outbound B which overwrites cfgPath, the stale 2s timer from A then deletes B's freshly-written running config. Hard to repro, but real.

2. Dangling timer holds the event loop open if the process exits in the gap before it fires.

Fix

connection/tunnel.js:563-583

Replace the unconditional 2s timer with:

• An idempotent deleteCfg() guarded by cfgDeleted
• proc.once('exit', deleteCfg) so the cfg is removed when V2Ray dies (covers fast-fail path)
• Inline deleteCfg() right after waitForPort(...) succeeds — at that point V2Ray has fully parsed the config
• A 5s unref()'d safety-net setTimeout for the edge case where neither happens before abort

Windows note: V2Ray may still have the file open when unlink runs. The existing try { } catch {} swallows EBUSY, and the exit handler picks it up once the process dies. No regression vs. the old timer behaviour there.

Test plan

• Connect to a V2Ray node, verify SOCKS5 proxy works
• After connect, confirm <tmpdir>/sentinel-v2ray/config.json is gone
• Disconnect, confirm cfg is gone (was already covered by old code)
• Force a fast-fail outbound (e.g., wrong UUID): cfg should still be gone after the loop completes
• Abort mid-handshake (Ctrl+C / signal disconnect): no leaked cfg, no leaked timer