Raise avatar cap 64 to 128 KiB, pipeline checks encoded size

64 KiB rejected normal 128px PNGs. 128 KiB fits any 128x128 PNG
(raw <= 64 KiB, worst-case base64 ~95 KiB chars) while still
bounding abuse. PNG kept for transparency. Pipeline now measures
the encoded base64 against RelayConstants (was checking the wrong
variable with its own 512 KiB limit) and drops dead crop code.
Server policy, still v4. Trade noted: avatars ride the 1 Hz room
broadcast, uplink scales with cap; hash-reference follow-up later.

docs/ROADMAP.md

@@ -73,7 +73,7 @@ silence-timeout + reconnect loop. Never run: shaper chaos suite
 
 ## Phase 6 — Identity & social (PARTIAL)
 
-Shipped: names (32 cap), avatars (64 KiB, picker + crop), kick nudge
+Shipped: names (32 cap), avatars (128 KiB cap, 128 px PNG picker, transparency kept), kick nudge
 + reason, feed attribution. Open: real chat pane/history (schema
 only), sounds swap-in (wiring + NoopSfxService ready; pick
 flutter_soloud or equivalent, Kenney/ObsydianX/akx sources in