fix(desktop): support macOS runtime installation paths

[tulayha]

Summary

• make managed runtime dependency installation safe when the staged constraints file lives under a path containing spaces, including macOS Library/Application Support
• keep the constraints file local to the staging working directory and pass only its file name to bundled uv
• remove the non-Windows unused_mut warning from the Tauri build script
• update the validated Python dependency set: Ruff 0.16.1, cryptography 50.0.0, DBOS 2.29.0, and filelock 3.32.2

Root cause

Bundled uv 0.12 splits the value supplied to --constraints on spaces even when the operating system provides it as a single argument. On a fresh macOS setup, the absolute constraints path under Library/Application Support was therefore truncated to /Users/grayhat/Library/Application, causing package installation to fail with exit status 2.

The dependency invocation now runs from the staged constraints directory and supplies runtime-constraints.txt as a local file name. Existing staged-runtime cleanup and active-runtime rollback behavior remain unchanged.

Impact

Fresh macOS configuration can install the managed VidXP runtime from the standard application-support directory. Windows and Linux retain their existing runtime paths, while non-Windows builds no longer emit the build-script mutability warning.

The lockfile refresh intentionally excludes the broader Uvicorn, Tokenizers, and PyArrow upgrades. VidXP's exact 0.4.0-b.2 release marker is preserved.

Validation

• uv lock --check
• uvx --from ruff==0.16.1 ruff check src tests
• 145 focused Python tests covering packaging/version contracts, DBOS workflows and SQLite migrations, file-lock-backed workers and snapshots, API behavior, and authentication
• dependency installation confirmed cryptography 50.0.0, DBOS 2.29.0, and filelock 3.32.2
• the complete Python suite was also started locally but exceeded the two-minute command window without reporting a failure

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fix(desktop): install managed runtimes from macOS Application Support paths
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