perf: avoid refresh full pid tree when Procs::new()

[gaojunran]

fixes #439.

[greptile-apps]

Greptile Summary

This PR avoids a full sysinfo process-tree scan on Procs::new() and replaces the broad refresh_processes() calls scattered across the codebase with targeted refresh_pids(&[pid]) calls that only refresh the specific PIDs actually needed.

• Procs::new() now returns an empty struct; every call site that needs process data explicitly refreshes the relevant PIDs before querying, removing the hidden startup cost.
• A refresh_daemon_pids helper and a refresh_daemon_list_pids local helper are introduced to consolidate the common pattern of collecting daemon PIDs and refreshing only those.
• Precondition documentation is added to kill and kill_process_group making the required refresh-before-call contract explicit; watchers.rs retains its refresh_processes() call because it needs the full process tree for child-process resource aggregation via get_batch_group_stats.

Confidence Score: 5/5

Safe to merge — all call sites correctly refresh targeted PIDs before querying; the one path that still needs a full refresh (watchers.rs) is untouched.

Every is_running, title(), and kill call site was audited and each has a refresh_pids immediately preceding it. The resource-monitoring watcher retains its full refresh_processes() because it uses get_batch_group_stats over the complete process tree. No silent no-ops or missed refreshes were found in the changed paths.

No files require special attention.

Important Files Changed

Filename	Overview
src/procs.rs	Core change: Procs::new() no longer pre-populates sysinfo; adds refresh_daemon_pids helper and precondition docs on kill/kill_process_group.
src/supervisor/lifecycle.rs	Adds refresh_pids after daemon spawn (before upsert_daemon reads title()); replaces full refresh with targeted PID check in stop path.
src/supervisor/mod.rs	Fixes implicit dependency on stale PROCS state in start_if_not_running and run; adds explicit targeted refresh before each is_running/title() call.
src/tui/app.rs	TUI stats refresh now targets only daemon root PIDs instead of all processes; consistent with get_stats which only examines the root PID anyway.
src/web/routes/daemons.rs	Extracts refresh_daemon_list_pids helper; replaces all broad refreshes with targeted ones; show now reads StateFile earlier to get the PID before refreshing.
src/cli/supervisor/mod.rs	Adds refresh_pids(&[existing_pid]) before is_running in kill_or_stop, satisfying the new precondition contract.
src/cli/wait.rs	Moves refresh to loop start and replaces broad refresh_processes with targeted refresh_pids; semantically equivalent and more efficient.
src/web/routes/index.rs	Reads StateFile before calling refresh_daemon_pids so only managed daemon PIDs are refreshed on each page render.

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