Add viewport-aware UI and ESP32-S3 support

[siwei-yuan]

Summary

This PR contains two changes:

1. Make Pocket Pi Views adapt to the logical viewport reported by each host.
2. Add the Waveshare ESP32-S3-Touch-LCD-4.3 firmware host.

Viewport-aware UI

• Pass one positive host Viewport through AppSupervisor to every System and ordinary App View Guest.
• Expose the immutable viewport through View SDK API 2.
• Scale geometry from the portrait and landscape reference canvases while keeping fixed readable font slots and physical touch minimums.
• Move reusable navigation, scroll, action-button and sparkline geometry into the shared View SDK.
• Update Pi Agent, Exa and Robinhood to use the same viewport-aware SDK without board-specific App forks.
• Let the simulator accept arbitrary WIDTHxHEIGHT viewports for UI validation.

ESP32-S3 firmware

• Add a board host for the 800x480 RGB panel with a rotated 480x800 logical viewport, GT911 touch and integrated Wi-Fi.
• Keep the shared AgentOS host loop, storage, transport and App lifecycle in firmware/esp32-common.
• Use PocketJS retained damage rendering, two PSRAM framebuffers, frame-complete presentation and board-local RGB565 rotation.
• Keep QuickJS heaps and large workers in PSRAM while reserving internal RAM for the runtime task and render stripe.
• Add reproducible ESP-IDF component locks, flash layout and one cargo xtask build entry.
• Keep the BSP limited to panel, touch, backlight and flash-dispatcher mechanisms; no LVGL runtime is included.

Validation

• cargo fmt checks
• git diff --check
• cargo clippy --workspace --all-targets -- -D warnings
• cargo build --workspace --all-targets
• cargo test --workspace: 54 passed
• bun test apps/pi-agent/text.test.js: 3 passed, 18 assertions
• cargo xtask build esp32-p4-sim
• cargo xtask build esp32-p4
• cargo xtask build esp32-s3
• Shell syntax checks for the ESP32-S3 compiler wrappers

Physical ESP32-S3 validation covers boot, 480x800 scanout, GT911 touch, integrated Wi-Fi, workspace Tool Calls, ordinary App installation and an Exa request. Long-running latency, display stability and memory-pressure testing remain separate physical acceptance work.

Architecture

ESP32-P4 remains the reference target. ESP32-P4 and ESP32-S3 share the same AgentOS, App sources, View SDK and runtime mechanisms; only their board adapters, viewport, display path, touch mapping and Wi-Fi hardware differ.