* fix: never surface coding-agent scratch worktrees in the sidebar
Sub-agent runs (e.g. Claude Code worktree isolation) create throwaway
git worktrees at tool-internal paths like <repo>/.claude/worktrees/.
These showed up as workspace rows for repos whose non-Orca worktree
visibility is 'show', and would otherwise ping the discovery card and
new-worktrees inbox on every fan-out.
Classify them as 'agent-scratch' via a curated path-segment matcher and
suppress them unconditionally: sidebar, discovery card, inbox, dialog
counts, add-handoff reveal trigger, and the metadata fallback. Selected
checkouts and explicitly imported paths still win.
Fixes#9388
* fix: preserve scratch worktree visibility boundaries
* fix: hide scratch worktrees from linked checkouts
* docs: explain scratch root normalization
