Letterboxed viewports, multi-identity sign-in, rest at the teahouse

Every platform now letterboxes to a real ratio. iOS and Android run at 19.5:9 (modern phone aspect), web runs at 16:9 (the typical browser shape). The hero strip and side panels size as fractions of the letterboxed viewport so they sit inside the safe area on a tall phone and don't sprawl across an ultrawide monitor. Same UI scales cleanly from a portrait phone to a desktop browser without pieces drifting.

Multi-identity linking is in. A player who started with Google sign-in can attach Apple later (and vice versa) — both identities resolve to the same account record. If the secondary identity is already attached to a different account, the linking flow surfaces a conflict-resolution screen instead of silently failing. The auth schema that landed in 2.0.0 already supported this; this is the player-facing flow on top.

Two content beats in Chapter 1. The teahouse now has a rest_trigger, so players can rest at the teahouse without first walking back out to the world map. The middle Old Road battle dropped from three enemies to two, and scene 3 lost one reward in turn — the fight was running long for the spot it sits at in the early arc.

Maya gains two first-time hints. When she hits Elemental Strain or Battle Fatigue for the first time, a hint surfaces explaining what the status does instead of leaving players to figure it out from a stat-bar shift. Same pattern as the existing tutorial hint slots — first encounter only.