Better handling skill depdenencies on ENV VAR. (#9017)

An experimental flow for env var skill dependencies. Skills can now
declare required env vars in SKILL.md; if missing, the CLI prompts the
user to get the value, and Core will store it in memory (eventually to a
local persistent store)
<img width="790" height="169" alt="image"
src="https://github.com/user-attachments/assets/cd928918-9403-43cb-a7e7-b8d59bcccd9a"
/>

codex-rs/app-server/src/bespoke_event_handling.rs

@@ -279,6 +279,7 @@ pub(crate) async fn apply_bespoke_event_handling(
                         header: question.header,
                         question: question.question,
                         is_other: question.is_other,
+                        is_secret: question.is_secret,
                         options: question.options.map(|options| {
                             options
                                 .into_iter()