feat(sandbox): add glob deny-read platform enforcement (#18096)

## Summary
- adds macOS Seatbelt deny rules for unreadable glob patterns
- expands unreadable glob matches on Linux and masks them in bwrap,
including canonical symlink targets
- keeps Linux glob expansion robust when `rg` is unavailable in minimal
or Bazel test environments
- adds sandbox integration coverage that runs `shell` and `exec_command`
with a `**/*.env = none` policy and verifies the secret contents do not
reach the model

## Linux glob expansion

```text
Prefer:   rg --files --hidden --no-ignore --glob <pattern> -- <search-root>
Fallback: internal globset walker when rg is not installed
Failure:  any other rg failure aborts sandbox construction
```

```
[permissions.workspace.filesystem]
glob_scan_max_depth = 2

[permissions.workspace.filesystem.":project_roots"]
"**/*.env" = "none"
```


This keeps the common path fast without making sandbox construction
depend on an ambient `rg` binary. If `rg` is present but fails for
another reason, the sandbox setup fails closed instead of silently
omitting deny-read masks.

## Platform support
- macOS: subprocess sandbox enforcement is handled by Seatbelt regex
deny rules
- Linux: subprocess sandbox enforcement is handled by expanding existing
glob matches and masking them in bwrap
- Windows: policy/config/direct-tool glob support is already on `main`
from #15979; Windows subprocess sandbox paths continue to fail closed
when unreadable split filesystem carveouts require runtime enforcement,
rather than silently running unsandboxed

## Stack
1. #15979 - merged: cross-platform glob deny-read
policy/config/direct-tool support for macOS, Linux, and Windows
2. This PR - macOS/Linux subprocess sandbox enforcement plus Windows
fail-closed clarification
3. #17740 - managed deny-read requirements

## Verification
- Added integration coverage for `shell` and `exec_command` glob
deny-read enforcement
- `cargo check -p codex-sandboxing -p codex-linux-sandbox --tests`
- `cargo check -p codex-core --test all`
- `cargo clippy -p codex-linux-sandbox -p codex-sandboxing --tests`
- `just bazel-lock-check`

---------

Co-authored-by: Codex <noreply@openai.com>

codex-rs/sandboxing/src/manager.rs

@@ -109,7 +109,6 @@ pub struct SandboxTransformRequest<'a> {
 #[derive(Debug)]
 pub enum SandboxTransformError {
     MissingLinuxSandboxExecutable,
-    UnreadableGlobPatternsUnsupported,
     #[cfg(target_os = "linux")]
     Wsl1UnsupportedForBubblewrap,
     #[cfg(not(target_os = "macos"))]
@@ -122,10 +121,6 @@ impl std::fmt::Display for SandboxTransformError {
             Self::MissingLinuxSandboxExecutable => {
                 write!(f, "missing codex-linux-sandbox executable path")
             }
-            Self::UnreadableGlobPatternsUnsupported => write!(
-                f,
-                "platform sandbox backend cannot enforce unreadable glob patterns"
-            ),
             #[cfg(target_os = "linux")]
             Self::Wsl1UnsupportedForBubblewrap => write!(f, "{WSL1_BWRAP_WARNING}"),
             #[cfg(not(target_os = "macos"))]
@@ -201,15 +196,6 @@ impl SandboxManager {
         );
         let effective_network_policy =
             effective_network_sandbox_policy(network_policy, additional_permissions.as_ref());
-        if matches!(
-            sandbox,
-            SandboxType::MacosSeatbelt | SandboxType::LinuxSeccomp
-        ) && !effective_file_system_policy
-            .get_unreadable_globs_with_cwd(sandbox_policy_cwd)
-            .is_empty()
-        {
-            return Err(SandboxTransformError::UnreadableGlobPatternsUnsupported);
-        }
         let mut argv = Vec::with_capacity(1 + command.args.len());
         argv.push(command.program);
         argv.extend(command.args.into_iter().map(OsString::from));