Scope command approvals by execution environment (#28738)

## Why

Command approval cache keys included the command and working directory,
but not the execution environment. An approval for `/workspace` locally
could therefore be reused for the same command and path on an executor.

## What changed

- Include the selected environment ID in shell and unified-exec approval
cache keys.
- Carry that ID through the normal command approval request so clients
can show which environment is being approved.
- Expose the environment through app-server as a required nullable
`environmentId` and show it in the inline TUI approval prompt.
- Keep older recorded approval events compatible when the environment is
absent.

For example, `echo ok` in local `/workspace` and `echo ok` in executor
`/workspace` now produce different approval keys and separate prompts.

## Scope

This PR does not change network approvals, Guardian review actions, MCP
elicitation, full-screen TUI rendering, or environment-ID validation.
Remote `shell_command` execution itself remains in #28722; this PR only
makes its approval key environment-aware.

codex-rs/tui/src/app/app_server_requests.rs

@@ -452,6 +452,7 @@ mod tests {
                 item_id: "call-1".to_string(),
                 started_at_ms: 0,
                 approval_id: Some("approval-1".to_string()),
+                environment_id: None,
                 reason: None,
                 network_approval_context: None,
                 command: Some("ls".to_string()),
@@ -791,6 +792,7 @@ mod tests {
                     item_id: "call-1".to_string(),
                     started_at_ms: 0,
                     approval_id: Some("approval-1".to_string()),
+                    environment_id: None,
                     reason: None,
                     network_approval_context: None,
                     command: Some("ls".to_string()),

codex-rs/tui/src/app/pending_interactive_replay.rs

@@ -615,6 +615,7 @@ mod tests {
                 item_id: call_id.to_string(),
                 started_at_ms: 0,
                 approval_id: approval_id.map(str::to_string),
+                environment_id: None,
                 reason: None,
                 network_approval_context: None,
                 command: Some("echo hi".to_string()),

codex-rs/tui/src/app/tests.rs

@@ -4690,6 +4690,7 @@ fn exec_approval_request(
             item_id: item_id.to_string(),
             started_at_ms: 0,
             approval_id: approval_id.map(str::to_string),
+            environment_id: None,
             reason: Some("needs approval".to_string()),
             network_approval_context: None,
             command: Some("echo hello".to_string()),

codex-rs/tui/src/app/thread_events.rs

@@ -488,6 +488,7 @@ mod tests {
                 item_id: item_id.to_string(),
                 started_at_ms: 0,
                 approval_id: approval_id.map(str::to_string),
+                environment_id: None,
                 reason: Some("needs approval".to_string()),
                 network_approval_context: None,
                 command: Some("echo hello".to_string()),

codex-rs/tui/src/app/thread_routing.rs

@@ -226,6 +226,7 @@ impl App {
                         .approval_id
                         .clone()
                         .unwrap_or_else(|| params.item_id.clone()),
+                    environment_id: params.environment_id.clone(),
                     command: params
                         .command
                         .as_deref()