chore(release): prepare v5.10.0

[SaladDay]

Summary

• bump CLI and lockfile metadata to v5.10.0
• publish the full release changelog and GitHub release notes, including community acknowledgements
• update the English and Chinese READMEs with concise descriptions of the shipped usage, sessions, MCP, and proxy capabilities
• remove completed session/usage implementation-plan documents and restore the changelog mirror
• keep the narrow Settings scrolling regression valid when longer release versions are ellipsized

Validation

• cargo fmt --check
• cargo check --locked (sandboxed configuration paths)
• cargo test --locked --lib cli::tui::ui::tests::settings_section_rows_do_not_shift_selection_or_break_narrow_scrolling -- --exact (sandboxed configuration paths)
• cargo metadata --locked --no-deps --format-version 1 confirms 5.10.0
• git diff --check
• root/docs changelog mirror check
• documentation prohibited-reference audit