Find tool binaries in per-user install dirs, and use that in status

After PATH, which_bin now searches each official installer's dir
(~/.grok/bin, ~/.kimi-code/bin, ~/.pi/agent/bin, plus the existing
Claude/OpenCode/Kilo ones), then ~/.local/bin and ~/.bun/bin for any tool.
A bun-installed omp was not found. `hcom status` checked PATH only for
Claude/Gemini/Codex/OpenCode/Kimi; it now uses the same lookup as launch.