## Why
Bubblewrap discovery probes executables before confinement. Excluding only the command's current directory leaves candidates in other writable roots eligible to run outside the sandbox.
## What changed
- Filter canonical `PATH` candidates using the filesystem policy and effective user permissions, including writable ancestors, symlinked roots, and full-disk write access. Preserve protected system installations while rejecting replaceable paths.
- Select the launcher with the command's permissions before the proc-mount preflight, retaining the bundled bubblewrap fallback.
- Use the effective permission profile and policy working directory for startup warning probes.
## Testing
Add unit coverage for writable roots, symlinks, read-only carveouts, replaceable parents, and full-disk policies. Add Linux integration tests showing writable `bwrap` candidates are neither probed nor launched, including when the command runs in a workspace subdirectory or uses managed networking with full-disk write access.
GitOrigin-RevId: 188c9f45e727eaace062f5abb1205dc23fdf3c51
viyatb-oai
7aa8f51049