feat: include available decisions in command approval requests (#12758)

Command-approval clients currently infer which choices to show from
side-channel fields like `networkApprovalContext`,
`proposedExecpolicyAmendment`, and `additionalPermissions`. That makes
the request shape harder to evolve, and it forces each client to
replicate the server's heuristics instead of receiving the exact
decision list for the prompt.

This PR introduces a mapping between `CommandExecutionApprovalDecision`
and `codex_protocol::protocol::ReviewDecision`:

```rust
impl From<CoreReviewDecision> for CommandExecutionApprovalDecision {
    fn from(value: CoreReviewDecision) -> Self {
        match value {
            CoreReviewDecision::Approved => Self::Accept,
            CoreReviewDecision::ApprovedExecpolicyAmendment {
                proposed_execpolicy_amendment,
            } => Self::AcceptWithExecpolicyAmendment {
                execpolicy_amendment: proposed_execpolicy_amendment.into(),
            },
            CoreReviewDecision::ApprovedForSession => Self::AcceptForSession,
            CoreReviewDecision::NetworkPolicyAmendment {
                network_policy_amendment,
            } => Self::ApplyNetworkPolicyAmendment {
                network_policy_amendment: network_policy_amendment.into(),
            },
            CoreReviewDecision::Abort => Self::Cancel,
            CoreReviewDecision::Denied => Self::Decline,
        }
    }
}
```

And updates `CommandExecutionRequestApprovalParams` to have a new field:

```rust
available_decisions: Option<Vec<CommandExecutionApprovalDecision>>
```

when, if specified, should make it easier for clients to display an
appropriate list of options in the UI.

This makes it possible for `CoreShellActionProvider::prompt()` in
`unix_escalation.rs` to specify the `Vec<ReviewDecision>` directly,
adding support for `ApprovedForSession` when approving a skill script,
which was previously missing in the TUI.

Note this results in a significant change to `exec_options()` in
`approval_overlay.rs`, as the displayed options are now derived from
`available_decisions: &[ReviewDecision]`.

## What Changed

- Add `available_decisions` to
[`ExecApprovalRequestEvent`](de00e932dd/codex-rs/protocol/src/approvals.rs (L111-L175)),
including helpers to derive the legacy default choices when older
senders omit the field.
- Map `codex_protocol::protocol::ReviewDecision` to app-server
`CommandExecutionApprovalDecision` and expose the ordered list as
experimental `availableDecisions` in
[`CommandExecutionRequestApprovalParams`](de00e932dd/codex-rs/app-server-protocol/src/protocol/v2.rs (L3798-L3807)).
- Thread optional `available_decisions` through the core approval path
so Unix shell escalation can explicitly request `ApprovedForSession` for
session-scoped approvals instead of relying on client heuristics.
[`unix_escalation.rs`](de00e932dd/codex-rs/core/src/tools/runtimes/shell/unix_escalation.rs (L194-L214))
- Update the TUI approval overlay to build its buttons from the ordered
decision list, while preserving the legacy fallback when
`available_decisions` is missing.
- Update the app-server README, test client output, and generated schema
artifacts to document and surface the new field.

## Testing

- Add `approval_overlay.rs` coverage for explicit decision lists,
including the generic `ApprovedForSession` path and network approval
options.
- Update `chatwidget/tests.rs` and app-server protocol tests to populate
the new optional field and keep older event shapes working.

## Developers Docs

- If we document `item/commandExecution/requestApproval` on
[developers.openai.com/codex](https://developers.openai.com/codex), add
experimental `availableDecisions` as the preferred source of approval
choices and note that older servers may omit it.

codex-rs/app-server-protocol/src/protocol/v2.rs

@@ -49,6 +49,7 @@ use codex_protocol::protocol::RateLimitWindow as CoreRateLimitWindow;
 use codex_protocol::protocol::ReadOnlyAccess as CoreReadOnlyAccess;
 use codex_protocol::protocol::RealtimeAudioFrame as CoreRealtimeAudioFrame;
 use codex_protocol::protocol::RejectConfig as CoreRejectConfig;
+use codex_protocol::protocol::ReviewDecision as CoreReviewDecision;
 use codex_protocol::protocol::SessionSource as CoreSessionSource;
 use codex_protocol::protocol::SkillDependencies as CoreSkillDependencies;
 use codex_protocol::protocol::SkillErrorInfo as CoreSkillErrorInfo;
@@ -741,7 +742,8 @@ pub struct ConfigEdit {
 pub enum CommandExecutionApprovalDecision {
     /// User approved the command.
     Accept,
-    /// User approved the command and future identical commands should run without prompting.
+    /// User approved the command and future prompts in the same session-scoped
+    /// approval cache should run without prompting.
     AcceptForSession,
     /// User approved the command, and wants to apply the proposed execpolicy amendment so future
     /// matching commands can run without prompting.
@@ -758,6 +760,27 @@ pub enum CommandExecutionApprovalDecision {
     Cancel,
 }
 
+impl From<CoreReviewDecision> for CommandExecutionApprovalDecision {
+    fn from(value: CoreReviewDecision) -> Self {
+        match value {
+            CoreReviewDecision::Approved => Self::Accept,
+            CoreReviewDecision::ApprovedExecpolicyAmendment {
+                proposed_execpolicy_amendment,
+            } => Self::AcceptWithExecpolicyAmendment {
+                execpolicy_amendment: proposed_execpolicy_amendment.into(),
+            },
+            CoreReviewDecision::ApprovedForSession => Self::AcceptForSession,
+            CoreReviewDecision::NetworkPolicyAmendment {
+                network_policy_amendment,
+            } => Self::ApplyNetworkPolicyAmendment {
+                network_policy_amendment: network_policy_amendment.into(),
+            },
+            CoreReviewDecision::Abort => Self::Cancel,
+            CoreReviewDecision::Denied => Self::Decline,
+        }
+    }
+}
+
 v2_enum_from_core! {
     pub enum NetworkApprovalProtocol from CoreNetworkApprovalProtocol {
         Http,
@@ -3802,6 +3825,11 @@ pub struct CommandExecutionRequestApprovalParams {
     #[serde(default, skip_serializing_if = "Option::is_none")]
     #[ts(optional = nullable)]
     pub proposed_network_policy_amendments: Option<Vec<NetworkPolicyAmendment>>,
+    /// Ordered list of decisions the client may present for this prompt.
+    #[experimental("item/commandExecution/requestApproval.availableDecisions")]
+    #[serde(default, skip_serializing_if = "Option::is_none")]
+    #[ts(optional = nullable)]
+    pub available_decisions: Option<Vec<CommandExecutionApprovalDecision>>,
 }
 
 impl CommandExecutionRequestApprovalParams {