Use Tuist manifest environment - #857

Summary

This updates OpenSwiftUI to use Tuist's new manifestEnvironment support from tuist/tuist#10705 instead of mirroring OpenSwiftUI environment variables with a TUIST_ prefix.

Tuist previously filtered manifest evaluation environments down to TUIST_*, CI, and a small allowlist. That meant tuist generate could not see the same OPENSWIFTUI_* values that SwiftPM and tuist install could see, so the project carried a local workaround: duplicated TUIST_OPENSWIFTUI_* values in mise.toml plus a Tuist_OpenSwiftUI env lookup domain in Package.swift.

Changes

• Bump the pinned Tuist CLI from 4.192.0 to 4.193.0, the release that includes manifestEnvironment.
• Configure Tuist.swift to forward OPENSWIFTUI_* into manifest evaluation.
• Remove the duplicated TUIST_OPENSWIFTUI_* values from mise.toml.
• Remove the Tuist_OpenSwiftUI compatibility domain from Package.swift.

Verification

Verified locally in the prepared worktree with local dependencies present:

MISE_TRUSTED_CONFIG_PATHS="$PWD/mise.toml" mise x -- tuist version
MISE_TRUSTED_CONFIG_PATHS="$PWD/mise.toml" mise x -- tuist install
MISE_TRUSTED_CONFIG_PATHS="$PWD/mise.toml" mise x -- tuist generate --no-open
git diff --check

tuist version reported 4.193.0. tuist install and tuist generate --no-open both succeeded. Generation still emits the existing static product side-effect warnings, but the project is generated successfully and the package manifest logs show the unprefixed OPENSWIFTUI_* values are visible without the old TUIST_ mirrors.