Batch macOS process discovery

[sdairs]

Summary

• resolve all ClickHouse process working directories with one batched lsof call on macOS
• parse lsof -Fn PID/path records and retain valid records if another process exits during discovery
• preserve the Linux /proc/<pid>/cwd fast path and add focused parser coverage

Why

Process discovery previously launched one lsof subprocess per process named clickhouse. On agent-heavy machines with many clickhouse-local or chDB processes, that made local commands stall for tens of seconds even when none of those processes belonged to the current project.

Impact

macOS discovery now pays the lsof startup cost once regardless of the number of ClickHouse processes. The CLI surface and Linux behavior are unchanged.

Stack

This PR is stacked on #347 and should be reviewed as the delta from codex/issue-337-org-autodetect.

Closes #329.

Validation

• cargo fmt --all --check
• cargo build -p clickhousectl --all-targets
• cargo test -p clickhousectl (570 tests)
• cargo clippy -p clickhousectl --all-targets -- -D warnings
• verified batched two-PID lsof -Fn output on macOS

[Copilot]

Pull request overview

This PR improves local ClickHouse server discovery performance on macOS by resolving all candidate process working directories in a single lsof invocation, while preserving the Linux /proc/<pid>/cwd fast path. It also adds focused unit coverage for parsing batched lsof -Fn output so discovery remains robust when some PIDs disappear during inspection.

Changes:

• Batch macOS cwd discovery into one lsof -a -d cwd -Fn -p <pid1,pid2,...> call and parse per-PID records (p<pid> / n<path>).
• Adjust discovery flow to precompute a PID→cwd map and pass cwd into inspect_process (instead of resolving per-PID inline).
• Add parser tests for correct attribution and malformed/incomplete record handling.

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