feat: introduce Permissions (#11633)

## Why
We currently carry multiple permission-related concepts directly on
`Config` for shell/unified-exec behavior (`approval_policy`,
`sandbox_policy`, `network`, `shell_environment_policy`,
`windows_sandbox_mode`).

Consolidating these into one in-memory struct makes permission handling
easier to reason about and sets up the next step: supporting named
permission profiles (`[permissions.PROFILE_NAME]`) without changing
behavior now.

This change is mostly mechanical: it updates existing callsites to go
through `config.permissions`, but it does not yet refactor those
callsites to take a single `Permissions` value in places where multiple
permission fields are still threaded separately.

This PR intentionally **does not** change the on-disk `config.toml`
format yet and keeps compatibility with legacy config keys.

## What Changed
- Introduced `Permissions` in `core/src/config/mod.rs`.
- Added `Config::permissions` and moved effective runtime permission
fields under it:
  - `approval_policy`
  - `sandbox_policy`
  - `network`
  - `shell_environment_policy`
  - `windows_sandbox_mode`
- Updated config loading/building so these effective values are still
derived from the same existing config inputs and constraints.
- Updated Windows sandbox helpers/resolution to read/write via
`permissions`.
- Threaded the new field through all permission consumers across core
runtime, app-server, CLI/exec, TUI, and sandbox summary code.
- Updated affected tests to reference `config.permissions.*`.
- Renamed the struct/field from
`EffectivePermissions`/`effective_permissions` to
`Permissions`/`permissions` and aligned variable naming accordingly.

## Verification
- `just fix -p codex-core -p codex-tui -p codex-cli -p codex-app-server
-p codex-exec -p codex-utils-sandbox-summary`
- `cargo build -p codex-core -p codex-tui -p codex-cli -p
codex-app-server -p codex-exec -p codex-utils-sandbox-summary`

codex-rs/core/src/tools/handlers/collab.rs

@@ -818,11 +818,12 @@ fn build_agent_shared_config(
     config.model_reasoning_summary = turn.reasoning_summary;
     config.developer_instructions = turn.developer_instructions.clone();
     config.compact_prompt = turn.compact_prompt.clone();
-    config.shell_environment_policy = turn.shell_environment_policy.clone();
+    config.permissions.shell_environment_policy = turn.shell_environment_policy.clone();
     config.codex_linux_sandbox_exe = turn.codex_linux_sandbox_exe.clone();
     config.cwd = turn.cwd.clone();
-    config.approval_policy = Constrained::allow_only(AskForApproval::Never);
+    config.permissions.approval_policy = Constrained::allow_only(AskForApproval::Never);
     config
+        .permissions
         .sandbox_policy
         .set(turn.sandbox_policy.clone())
         .map_err(|err| {
@@ -1717,8 +1718,8 @@ mod tests {
         turn.cwd = temp_dir.path().to_path_buf();
         turn.codex_linux_sandbox_exe = Some(PathBuf::from("/bin/echo"));
         turn.sandbox_policy = pick_allowed_sandbox_policy(
-            &turn.config.sandbox_policy,
-            turn.config.sandbox_policy.get().clone(),
+            &turn.config.permissions.sandbox_policy,
+            turn.config.permissions.sandbox_policy.get().clone(),
         );
 
         let config = build_agent_spawn_config(&base_instructions, &turn, 0).expect("spawn config");
@@ -1730,14 +1731,16 @@ mod tests {
         expected.model_reasoning_summary = turn.reasoning_summary;
         expected.developer_instructions = turn.developer_instructions.clone();
         expected.compact_prompt = turn.compact_prompt.clone();
-        expected.shell_environment_policy = turn.shell_environment_policy.clone();
+        expected.permissions.shell_environment_policy = turn.shell_environment_policy.clone();
         expected.codex_linux_sandbox_exe = turn.codex_linux_sandbox_exe.clone();
         expected.cwd = turn.cwd.clone();
         expected
+            .permissions
             .approval_policy
             .set(AskForApproval::Never)
             .expect("approval policy set");
         expected
+            .permissions
             .sandbox_policy
             .set(turn.sandbox_policy)
             .expect("sandbox policy set");
@@ -1777,14 +1780,16 @@ mod tests {
         expected.model_reasoning_summary = turn.reasoning_summary;
         expected.developer_instructions = turn.developer_instructions.clone();
         expected.compact_prompt = turn.compact_prompt.clone();
-        expected.shell_environment_policy = turn.shell_environment_policy.clone();
+        expected.permissions.shell_environment_policy = turn.shell_environment_policy.clone();
         expected.codex_linux_sandbox_exe = turn.codex_linux_sandbox_exe.clone();
         expected.cwd = turn.cwd.clone();
         expected
+            .permissions
             .approval_policy
             .set(AskForApproval::Never)
             .expect("approval policy set");
         expected
+            .permissions
             .sandbox_policy
             .set(turn.sandbox_policy)
             .expect("sandbox policy set");