feat(mcp): hide background startup status by default [1 of 5]

[fcoury-oai]

Why

Optional MCP servers can take noticeable time to initialize. Startup should not block ordinary prompts or fill the TUI with background diagnostics unless the user explicitly opts into that debugging surface.

What Changed

• Add [tui] show_mcp_startup_status = true as an opt-in diagnostic setting. The default is false.
• Read ready or cached MCP tool inventory without waiting for unresolved optional servers.
• Wait for MCP readiness when a turn explicitly selects an app or plugin dependency and emit an actionable warning if that dependency is unavailable.
• Keep existing eager inventory behavior available for callers that require it.

Stack

1. feat(mcp): hide background startup status by default [1 of 5] #25212 background MCP startup status (this PR)
2. #25213 atomic startup header handoff
3. #25214 explicit MCP dependency readiness
4. #25211 lazy tool-search registration
5. #24987 pending MCP inventory integration

How to Test

1. Configure a slow optional MCP server and start the TUI with default configuration.
2. Confirm the composer remains usable without showing MCP startup progress or background failure history.
3. Set [tui] show_mcp_startup_status = true, restart, and confirm startup progress and diagnostics are visible again.
4. Explicitly invoke a configured app or plugin backed by a failing MCP server and confirm an actionable dependency warning appears.

Targeted coverage:

• just test -p codex-mcp
• just test -p codex-tui mcp_startup_status_is_hidden_by_default