Documents the Checks/ + SystemCheckPage feature (gating rule, check list,
FreshInstall-only placement) and the ExecutableResolver/.cmd-shim wiring in
ClaudeDo.Worker's ClaudeCliPreflight/ClaudeProcess. Adds docs/explore-notes/installer-preflight.md
(bumped/corrected against the actual implementation) and links it from the
explore-notes README and root CLAUDE.md.
The underlying code lives only on unmerged task branches (06aca9b3.../40272c0b...),
not on main yet, and two follow-up features ("Claude Help Me" button, Config-mode
Diagnose section) were never implemented because they blocked on that same missing
merge. Both gaps are called out explicitly in the new docs and in docs/open.md's
verification checklist, instead of being asserted as done.
mika kuns