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/core/src/session/mod.rs

@@ -2039,6 +2039,7 @@ impl Session {
         turn_context: &TurnContext,
         call_id: String,
         approval_id: Option<String>,
+        environment_id: Option<String>,
         command: Vec<String>,
         cwd: AbsolutePathBuf,
         reason: Option<String>,
@@ -2091,6 +2092,7 @@ impl Session {
             call_id,
             approval_id,
             turn_id: turn_context.sub_id.clone(),
+            environment_id,
             started_at_ms: now_unix_timestamp_ms(),
             command,
             cwd,