core: remove unused permissions cwd plumbing

[bolinfest]

Why

compile_scoped_filesystem_pattern() accepted a _policy_cwd parameter even though scoped glob compilation no longer uses the policy working directory. Keeping that unused argument forced the surrounding permissions compilation path to keep forwarding policy_cwd through call sites that did not need it, making the API look more dependent on cwd resolution than it is.

What changed

Removed the unused cwd parameter from compile_scoped_filesystem_pattern() and the callers that only forwarded it: compile_filesystem_permission(), compile_permission_profile(), and compile_permission_profile_selection(). Workspace root resolution still keeps policy_cwd, because that path still resolves relative roots against the active policy cwd.

Relevant code: codex-rs/core/src/config/permissions.rs.

Verification

• just test -p codex-core config::permissions
• just test -p codex-core was also run after building test_stdio_server; it passed the touched permissions coverage but still reported unrelated existing failures in cli_stream and shell snapshot tests.