fix(tui): route mcp list paste into search

[OnlyYu1996]

Fixes PlatformNetwork/bounty-challenge#53265.

Summary

• Route pasted text in the MCP Servers list modal into the same searchable SelectionList used by typed filtering.
• Make the modal consume list-mode paste events so clipboard text no longer falls through to the hidden session composer.
• Add a regression test covering paste updating the list search query and selected filtered server.

Validation

• rustfmt +stable --edition 2024 --check src/cortex-tui/src/modal/mcp_manager/mod.rs src/cortex-tui/src/widgets/selection_list.rs
• cargo +stable test --package cortex-tui test_list_mode_paste_updates_search_query -- --nocapture
• git diff --check

Note: cargo +stable fmt --package cortex-tui --check is currently blocked by an unrelated existing formatting diff in src/cortex-tui/src/question.rs; the touched files pass rustfmt directly.

[greptile-apps]

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