core tests: submit turns with permission profiles (#20010)

## Summary

- Add `PermissionProfile`-based turn submission helpers to
`core_test_support`, while keeping the legacy `SandboxPolicy` helper for
tests that intentionally exercise legacy fallback behavior.
- Switch the default `TestCodex::submit_turn()` path to send a real
`PermissionProfile` plus the required legacy compatibility projection in
`Op::UserTurn`.
- Migrate straightforward app/search/shell/truncation tests from
`SandboxPolicy::{DangerFullAccess, ReadOnly}` to
`PermissionProfile::{Disabled, read_only}`.
- Add a TUI compatibility projection helper for legacy app-server fields
so non-legacy writable roots are preserved instead of being downgraded
to read-only.
- Fix remote start/resume/fork sandbox-mode projection to classify any
managed profile with writable roots as workspace-write, not only
profiles that can write `cwd`.
- Reduce `SandboxPolicy` references in `codex-rs/core/tests` from 47
files to 41 files without changing production behavior.

## Testing

- `cargo check -p codex-core --tests`
- `cargo test -p codex-tui
compatibility_profile_preserves_unbridgeable_write_roots`
- `cargo test -p codex-tui
sandbox_mode_preserves_non_cwd_write_roots_for_remote_sessions`
- `just fmt`
- `just fix -p core_test_support`
- `just fix -p codex-core`

codex-rs/tui/src/app_command.rs

@@ -23,6 +23,8 @@ use codex_protocol::user_input::UserInput;
 use serde::Serialize;
 use serde_json::Value;
 
+use crate::permission_compat::legacy_compatible_permission_profile;
+
 #[derive(Debug, Clone, PartialEq, Serialize)]
 pub(crate) struct AppCommand(Op);
 
@@ -148,18 +150,12 @@ impl AppCommand {
         collaboration_mode: Option<CollaborationMode>,
         personality: Option<Personality>,
     ) -> Self {
-        let sandbox_policy = permission_profile
+        let legacy_profile =
+            legacy_compatible_permission_profile(&permission_profile, cwd.as_path());
+        let sandbox_policy = legacy_profile
             .to_legacy_sandbox_policy(cwd.as_path())
             .unwrap_or_else(|err| {
-                tracing::warn!(
-                    %err,
-                    "permission profile cannot be projected to legacy UserTurn sandbox; using read-only compatibility fallback"
-                );
-                PermissionProfile::read_only()
-                    .to_legacy_sandbox_policy(cwd.as_path())
-                    .unwrap_or_else(|err| {
-                        unreachable!("read-only permissions must be legacy-compatible: {err}")
-                    })
+                unreachable!("legacy-compatible permissions must project to legacy policy: {err}")
             });
         Self(Op::UserTurn {
             items,