To fix the occurences where the End event is received after the listener
stopped listenning

A recent change in commit ccba737 modified the styling of the
placeholder text (e.g. "Implement {feature}") in the input box of the
CLI, changing it from non-italic to italic. I think this was likely
unintentional. It results in a bad display appearance on some terminal
emulators, and several users have complained about it.

This change switches back to non-italic styling, restoring the older
behavior.

It addresses #9262

We’re introducing a new SKILL.toml to hold skill metadata so Codex can
deliver a richer Skills experience.

Initial focus is the interface block:
```
[interface]
display_name = "Optional user-facing name"
short_description = "Optional user-facing description"
icon_small = "./assets/small-400px.png"
icon_large = "./assets/large-logo.svg"
brand_color = "#3B82F6"
default_prompt = "Optional surrounding prompt to use the skill with"
```

All fields are exposed via the app server API.
display_name and short_description are consumed by the TUI.

moving `web_search` rollout serverside, so need a way to explicitly
disable search + signal eligibility from the client.

- Add `x‑oai‑web‑search‑eligible` header that signifies whether the
request can have web search.
- Only attach the `web_search` tool when the resolved `WebSearchMode` is
`Live` or `Cached`.

Revert #9049 behavior so empty paste events no longer trigger a
clipboard image read.

## Summary

- When a user accepts an MCP elicitation request, send `content:
Some(json!({}))` instead of `None`
- MCP servers that use elicitation expect content to be present when
action is Accept
- This matches the expected behavior shown in tests at
`exec-server/tests/common/lib.rs:171`

## Root Cause

In `codex-rs/core/src/codex.rs`, the `resolve_elicitation` function
always sent `content: None`:

```rust
let response = ElicitationResponse {
    action,
    content: None,  // Always None, even for Accept
};
```

## Fix

Send an empty object when accepting:

```rust
let content = match action {
    ElicitationAction::Accept => Some(serde_json::json!({})),
    ElicitationAction::Decline | ElicitationAction::Cancel => None,
};
```

## Test plan

- [x] Code compiles with `cargo check -p codex-core`
- [x] Formatted with `just fmt`
- [ ] Integration test `accept_elicitation_for_prompt_rule` (requires
MCP server binary)

Fixes #9053

- Skill metadata can now be defined in `SKILL.toml` (names, descriptions, icons, brand color, default prompt) and surfaced in the app server and TUI (#9125)
- Clients can explicitly disable web search and signal eligibility via a header to align with server-side rollout controls (#9249)

## Bug Fixes
- Accepting an MCP elicitation now sends an empty JSON payload instead of null to satisfy servers expecting content (#9196)
- Input prompt placeholder styling is back to non-italic to avoid terminal rendering issues (#9307)
- Empty paste events no longer trigger clipboard image reads (#9318)
- Unified exec cleans up background processes to prevent late End events after listeners stop (#9304)

## Chores
- Refresh the orchestrator prompt to improve internal routing behavior (#9301)
- Reduce noisy `needs_follow_up` error logging (#9272)

## Changelog

Full Changelog: rust-v0.85.0...rust-v0.86.0

- #9301 chore: better orchestrator prompt @jif-oai
- #9304 nit: clean unified exec background processes @jif-oai
- #9307 Revert recent styling change for input prompt placeholder text @etraut-openai
- #9125 Support SKILL.toml file. @xl-openai
- #9249 [search] allow explicitly disabling web search @sayan-oai
- #9272 remove needs_follow_up error log @pap-openai
- #9318 Revert empty paste image handling @aibrahim-oai
- #9196 fix: send non-null content on elicitation Accept @yuvrajangadsingh