feat: improved AEC, keyboard shortcuts, dedup participants, dev-fast profile

AEC improvements:
- Reduce echo tail from 100ms to 30ms (3.3x faster, suited for laptops)
- Add double-talk detection: freeze adaptation when near-end speaks
- Add residual echo suppression
- Disable AEC by default in --android mode (macOS has built-in AEC)

CLI features:
- Keyboard shortcuts: m=mic mute, s=speaker mute, q=quit (raw terminal mode)
- Dedup participants in RoomUpdate display (same fingerprint+alias shown once)
- Add dev-fast profile (opt-level 2 with incremental compilation)

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

Cargo.toml

@@ -54,6 +54,12 @@ wzp-crypto = { path = "crates/wzp-crypto" }
 wzp-transport = { path = "crates/wzp-transport" }
 wzp-client = { path = "crates/wzp-client" }
 
+# Fast dev profile: optimized but with debug info and incremental compilation.
+# Use with: cargo run --profile dev-fast
+[profile.dev-fast]
+inherits = "dev"
+opt-level = 2
+
 # Optimize heavy compute deps even in debug builds —
 # real-time audio needs < 20ms per frame, impossible unoptimized.
 [profile.dev.package.nnnoiseless]