internal/checker+gui: remove voice-srv test (Discord doesn't expose regional voice servers via public DNS)

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

docs/superpowers/specs/2026-05-01-checker-design.md

@@ -56,11 +56,6 @@ type Config struct {
     // voice-quality burst tuning
     VoiceBurstCount    int           // default 30
     VoiceBurstInterval time.Duration // default 20ms
-
-    // voice-srv probe — empty list means "use the built-in default
-    // (russia/russia2/frankfurt/europe/singapore/japan/us-east/us-west/
-    // brazil/india/hongkong/southkorea/sydney/southafrica/dubai/atlanta).discord.media"
-    VoiceServerHostnames []string
 }
 
 // StatusWarn is a "soft pass" — the test technically succeeded but
@@ -93,7 +88,6 @@ Sequential. Each test reuses sockets opened by previous tests when sensible.
 | `connect` | SOCKS5 CONNECT to `gateway.discord.gg:443` (ATYP=03 domain). Reads 10 bytes. Pass = REP=0x00. | REP != 0 (0x05 = connection refused, etc) / timeout | skipped if `greet`/`auth` failed |
 | `udp` | UDP ASSOCIATE: opens **second** TCP control channel, redoes greeting+auth there, sends `05 03 00 01 00000000 0000`, reads 10-byte reply. Pass = REP=0x00 + valid relay endpoint in BND.ADDR/BND.PORT. | REP=0x07 (cmd unsupported), other REP, short read | skipped if `greet` failed |
 | `voice-quality` | Through the relay: send `VoiceBurstCount` (default 30) STUN binding requests to `cfg.StunServer`, spaced `VoiceBurstInterval` (default 20ms). Listen until `last_send + 1.5*PerTestTimeout`. Compute `loss%`, `jitter` (mean abs delta of inter-arrival deltas, à la RFC 3550 simplified), `p50 RTT`. Metric = `"loss=2% jitter=14ms p50=42ms"`. **Pass** = loss ≤ 5% AND jitter ≤ 30ms AND p50 ≤ 250ms. **Warn-pass** (status=passed but Hint set) = loss ≤ 15% AND jitter ≤ 60ms — voice will work with audible glitches. **Fail** = anything worse. | loss > 15% OR jitter > 60ms OR p50 > 400ms OR no replies at all | skipped if `udp` failed |
-| `voice-srv` | Probe Discord voice servers. Concurrently DNS-resolve a hardcoded list of `<region>.discord.media` hostnames (`russia`, `russia2`, `frankfurt`, `europe`, `singapore`, `japan`, `us-east`, `us-west`, `brazil`, `india`, `hongkong`, `southkorea`, `sydney`, `southafrica`, `dubai`, `atlanta`) using OS resolver, 2s budget. For every resolved hostname: SOCKS5 CONNECT through proxy to `host:443` with 1s dial timeout, run them concurrently with a small worker pool (8). Metric = `"<N> regions reachable: russia, frankfurt, europe"` (top 3). **Pass** = ≥ 1 region reachable. **Warn-pass** = 0 reachable but ≥ 1 resolved (proxy filters Discord media IPs even though DNS works) — Hint will warn that voice may not work despite checks 1-5 passing. **Fail** = 0 hostnames resolved at all (DNS broken or Discord changed naming) | 0 hostnames resolved at all | skipped if `connect` failed |
 | `api` | TCP CONNECT through the proxy to `discord.com:443`, do a tiny HTTPS GET `/api/v9/gateway`. Pass = HTTP 200 or 401 (Discord returns 401 unauthenticated, that still proves reachability). | non-200/401 / TLS handshake failed / connect refused | skipped if `connect` failed |
 
 For each fail, the `Hint` field carries a Russian explanation (the GUI is