chore: remove skill metadata from command approval payloads (#15906)

## Why

This is effectively a follow-up to
[#15812](https://github.com/openai/codex/pull/15812). That change
removed the special skill-script exec path, but `skill_metadata` was
still being threaded through command-approval payloads even though the
approval flow no longer uses it to render prompts or resolve decisions.

Keeping it around added extra protocol, schema, and client surface area
without changing behavior.

Removing it keeps the command-approval contract smaller and avoids
carrying a dead field through app-server, TUI, and MCP boundaries.

## What changed

- removed `ExecApprovalRequestSkillMetadata` and the corresponding
`skillMetadata` field from core approval events and the v2 app-server
protocol
- removed the generated JSON and TypeScript schema output for that field
- updated app-server, MCP server, TUI, and TUI app-server approval
plumbing to stop forwarding the field
- cleaned up tests that previously constructed or asserted
`skillMetadata`

## Testing

- `cargo test -p codex-app-server-protocol`
- `cargo test -p codex-protocol`
- `cargo test -p codex-app-server-test-client`
- `cargo test -p codex-mcp-server`
- `just argument-comment-lint`

codex-rs/core/src/codex.rs

@@ -75,7 +75,6 @@ use codex_otel::current_span_w3c_trace_context;
 use codex_otel::set_parent_from_w3c_trace_context;
 use codex_protocol::ThreadId;
 use codex_protocol::approvals::ElicitationRequestEvent;
-use codex_protocol::approvals::ExecApprovalRequestSkillMetadata;
 use codex_protocol::approvals::ExecPolicyAmendment;
 use codex_protocol::approvals::NetworkPolicyAmendment;
 use codex_protocol::approvals::NetworkPolicyRuleAction;
@@ -2897,7 +2896,6 @@ impl Session {
         network_approval_context: Option<NetworkApprovalContext>,
         proposed_execpolicy_amendment: Option<ExecPolicyAmendment>,
         additional_permissions: Option<PermissionProfile>,
-        skill_metadata: Option<ExecApprovalRequestSkillMetadata>,
         available_decisions: Option<Vec<ReviewDecision>>,
     ) -> ReviewDecision {
         //  command-level approvals use `call_id`.
@@ -2951,7 +2949,6 @@ impl Session {
             proposed_execpolicy_amendment,
             proposed_network_policy_amendments,
             additional_permissions,
-            skill_metadata,
             available_decisions: Some(available_decisions),
             parsed_cmd,
         });

codex-rs/core/src/codex_delegate.rs

@@ -436,7 +436,6 @@ async fn handle_exec_approval(
         network_approval_context,
         proposed_execpolicy_amendment,
         additional_permissions,
-        skill_metadata,
         available_decisions,
         ..
     } = event;
@@ -480,7 +479,6 @@ async fn handle_exec_approval(
                 network_approval_context,
                 proposed_execpolicy_amendment,
                 additional_permissions,
-                skill_metadata,
                 available_decisions,
             ),
             parent_session,

codex-rs/core/src/codex_delegate_tests.rs

@@ -286,7 +286,6 @@ async fn handle_exec_approval_uses_call_id_for_guardian_review_and_approval_id_f
                     proposed_execpolicy_amendment: None,
                     proposed_network_policy_amendments: None,
                     additional_permissions: None,
-                    skill_metadata: None,
                     available_decisions: Some(vec![
                         ReviewDecision::Approved,
                         ReviewDecision::Abort,

codex-rs/core/src/tools/network_approval.rs

@@ -384,7 +384,6 @@ impl NetworkApprovalService {
                     Some(network_approval_context.clone()),
                     /*proposed_execpolicy_amendment*/ None,
                     /*additional_permissions*/ None,
-                    /*skill_metadata*/ None,
                     available_decisions,
                 )
                 .await

codex-rs/core/src/tools/runtimes/shell.rs

@@ -184,7 +184,6 @@ impl Approvable<ShellRequest> for ShellRuntime {
                             .proposed_execpolicy_amendment()
                             .cloned(),
                         req.additional_permissions.clone(),
-                        /*skill_metadata*/ None,
                         available_decisions,
                     )
                     .await

codex-rs/core/src/tools/runtimes/shell/unix_escalation.rs

@@ -426,7 +426,6 @@ impl CoreShellActionProvider {
                         /*network_approval_context*/ None,
                         /*proposed_execpolicy_amendment*/ None,
                         additional_permissions,
-                        /*skill_metadata*/ None,
                         Some(vec![ReviewDecision::Approved, ReviewDecision::Abort]),
                     )
                     .await

codex-rs/core/src/tools/runtimes/unified_exec.rs

@@ -161,7 +161,6 @@ impl Approvable<UnifiedExecRequest> for UnifiedExecRuntime<'_> {
                             .proposed_execpolicy_amendment()
                             .cloned(),
                         req.additional_permissions.clone(),
-                        /*skill_metadata*/ None,
                         available_decisions,
                     )
                     .await