fix: send non-null content on elicitation Accept

[yuvrajangadsingh]

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:

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

Fix

Send an empty object when accepting:

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

Test plan

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

Fixes #9053

[etraut-openai]

@codex review

[chatgpt-codex-connector]

Codex Review: Didn't find any major issues. Already looking forward to the next diff.

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[bolinfest]

Seems reasonable.

FYI, I did some related work on the MCP Inspector: modelcontextprotocol/inspector#926.