protocol: preserve glob scan depth in permission profiles (#18713)

## Why

#18274 made `PermissionProfile` the canonical file-system permissions
shape, but the round-trip from `FileSystemSandboxPolicy` to
`PermissionProfile` still dropped one piece of policy metadata:
`glob_scan_max_depth`.

That field is security-relevant for deny-read globs such as `**/*.env`.
On Linux, bubblewrap sandbox construction uses it to bound unreadable
glob expansion. If a profile copied from active runtime permissions
loses this value and is submitted back as an override, the resulting
`FileSystemSandboxPolicy` can behave differently even though the visible
permission entries look equivalent.

## What changed

- Add `glob_scan_max_depth` to protocol `FileSystemPermissions` and
preserve it when converting to/from `FileSystemSandboxPolicy`.
- Keep legacy `read`/`write` JSON for simple path-only permissions, but
force canonical JSON when glob scan depth is present so the metadata is
not silently dropped.
- Carry `globScanMaxDepth` through app-server
`AdditionalFileSystemPermissions`, generated JSON/TypeScript schemas,
and app-server/TUI conversion call sites.
- Preserve the metadata through sandboxing permission normalization,
merging, and intersection.
- Carry the merged scan depth into the effective
`FileSystemSandboxPolicy` used for command execution, so bounded
deny-read globs reach Linux bubblewrap materialization.

## Verification

- `cargo test -p codex-sandboxing glob_scan -- --nocapture`
- `cargo test -p codex-sandboxing policy_transforms -- --nocapture`
- `just fix -p codex-sandboxing`





---
[//]: # (BEGIN SAPLING FOOTER)
Stack created with [Sapling](https://sapling-scm.com). Best reviewed
with [ReviewStack](https://reviewstack.dev/openai/codex/pull/18713).
* #18288
* #18287
* #18286
* #18285
* #18284
* #18283
* #18282
* #18281
* #18280
* #18279
* #18278
* #18277
* #18276
* #18275
* __->__ #18713

codex-rs/app-server-protocol/schema/json/codex_app_server_protocol.schemas.json

@@ -16,6 +16,14 @@
             "null"
           ]
         },
+        "globScanMaxDepth": {
+          "format": "uint",
+          "minimum": 1.0,
+          "type": [
+            "integer",
+            "null"
+          ]
+        },
         "read": {
           "items": {
             "$ref": "#/definitions/v2/AbsolutePathBuf"