[codex] Fix GPUI example rendering and tooltip overlays

[cyrilmhansen]

Summary

Fix the current stable/Linux breakages that prevented the library and examples from being meaningfully evaluated.

What Changed

• vendor and patch adabraka-gpui locally so the crate builds without hard-requiring Linux tray/dbus support
• remove the default http feature from adabraka-ui so the default build no longer depends on system OpenSSL
• fix GPUI quad/shadow host-to-shader layout mismatches that caused missing button, toggle, card, and table chrome at runtime
• restore demo bootstrap in examples/demo.rs by initializing the library and icon base path
• replace the broken tooltip overlay path with a simpler in-tree absolute overlay that actually appears on hover

Root Cause

There were multiple independent regressions layered together:

• the current default feature set assumed native Linux/dbus and OpenSSL dependencies that are not required for the base library
• the forked GPUI renderer had ABI/layout mismatches between Rust-side structs and WGSL expectations, so quads rendered incorrectly even though text still appeared
• the tooltip implementation relied on a deferred anchored overlay path that no longer produced visible tooltips in this branch
• the main demo example was not initializing the library/icon path, making the showcase look more broken than it should

Validation

• cargo build
• cargo build --examples
• manual runtime checks of demo, button_styled_demo, card_styled_demo, and tooltip_styled_demo

Notes

This PR is still larger than ideal because the GPUI fixes are carried through a vendored adabraka-gpui patch under vendor/. A follow-up could split the GPUI renderer fixes into that fork directly.

[Augani]

Interesting