fix(codex): handle MCP tool approval elicitation separately

[pokoynik]

Problem

mcpServer/elicitation/request for MCP tool approvals could fall through Symphony's generic approval handling.

In practice, this caused Codex app-server turns to appear stuck while waiting on Linear MCP save_comment approvals. The runtime log showed the turn hanging on mcpServer/elicitation/request until timeout or shutdown.

Root cause

The client did not have dedicated handling for MCP tool approval elicitations. Because the payload contains approval-related metadata (_meta.codex_approval_kind = "mcp_tool_call"), it matched the generic approval path and replied with:

{ "approved": true }

But Codex app-server expects an MCP elicitation acceptance payload shaped like:

{ "action": "accept", "content": {}, "_meta": { "persist": ... } }

That meant the elicitation was not actually resolved, so the app-server kept waiting.

Fix

• add dedicated detection for mcpServer/elicitation/request with codex_approval_kind = "mcp_tool_call"
• reply with the expected MCP acceptance payload
• preserve persist semantics (always / session) from the elicitation metadata
• keep this handling ahead of the generic approval branch
• add regression coverage with a fake app-server scenario that verifies the accepted payload shape

Validation

I ran:

• corepack pnpm test
• corepack pnpm typecheck
• corepack pnpm build
• corepack pnpm exec biome check src/codex/app-server-client.ts tests/codex/app-server-client.test.ts tests/fixtures/codex-fake-server.mjs

All of the above passed locally.