Clarify local server lifecycle help

[sdairs]

Summary

• document exact canonical-CWD project scope and the inherited omitted-name policies for local ClickHouse server teardown
• give coding agents a named start, stop, and remove workflow, including generated-name retention and project cleanup via server stop-all
• contrast global ClickHouse version removal with project-local server-data removal in the README
• pin the rendered lifecycle help for scope, examples, selection behavior, and cleanup guidance

Closes #478

Tests

• clickhousectl local server --help
• clickhousectl local server start --help
• clickhousectl local server stop --help
• clickhousectl local server remove --help
• clickhousectl local server stop-all --help
• cargo fmt --all --check
• cargo test -p clickhousectl (639 unit tests plus all integration suites)
• cargo clippy -p clickhousectl --all-targets -- -D warnings

Stack

• Position: child 11 of 11 in gh-stack #519
• Base: Expose project scope in managed local client errors #518 (issue-467-client-project-scope-errors)
• Parent PR should merge first; this PR is not intended to merge independently.

[sdairs]

Addressed in c764b48.

• Removed the top-level agent-help sentence that restated the stop-all descriptor, while preserving the non-obvious lifecycle and omitted-name guidance.
• Removed the generated-name operational reminder from the README and updated the directly affected help assertion.
• Verified with cargo test -p clickhousectl local::cli::tests, cargo fmt --all --check, cargo check -p clickhousectl, and cargo clippy -p clickhousectl --all-targets -- -D warnings.