Move cert noise calibration into doppelganger scout

Instead of a separate cert_probe.go that duplicates the scout's TLS
connection logic, measure the cert chain size directly from the same
HTTPS connections the scout already makes.

Changes:
- Extend ScoutConnResult with payloadLen field
- Add Write interception to ScoutConn for handshake boundary detection
- Scout.learn() now computes cert size (sum of ApplicationData between
  CCS and first client Write) alongside inter-record durations
- Ganger aggregates cert sizes across raids and exposes NoiseParams()
  via atomic pointer for lock-free reads from proxy goroutines
- Proxy reads NoiseParams from Ganger on each handshake instead of
  probing at startup
- Remove cert_probe.go, disk cache, and related config options
  (noise-cache-path, noise-cache-ttl, noise-probe-count)

Falls back to legacy 2500-4700 range until the first scout raid
completes (typically within 1-2 seconds of startup).

internal/cli/run_proxy.go

@@ -267,10 +267,6 @@ func runProxy(conf *config.Config, version string) error { //nolint: funlen
 		DoppelGangerPerRaid: conf.Defense.Doppelganger.Repeats.Get(mtglib.DoppelGangerPerRaid),
 		DoppelGangerEach:    conf.Defense.Doppelganger.UpdateEach.Get(mtglib.DoppelGangerEach),
 		DoppelGangerDRS:     conf.Defense.Doppelganger.DRS.Get(false),
-
-		NoiseProbeCount: conf.Defense.Doppelganger.NoiseProbeCount.Get(0),
-		NoiseCacheTTL:   conf.Defense.Doppelganger.NoiseCacheTTL.Get(0),
-		NoiseCachePath:  conf.Defense.Doppelganger.NoiseCachePath,
 	}
 
 	proxy, err := mtglib.NewProxy(opts)