Rework the duplicate-id decision block from button rows into a shadcn
radio-group: split file path into name + folder, add original/copy
badges, show the per-row outcome (keeps id / new id), preselect the
likely original as canonical, and surface resolved/unresolved group
status.

Add shadcn radio-group and badge primitives.

Run a non-blocking, read-only vault doctor preview after app load (in
idle) and show a sonner with a "Review" action when sync conflicts are
found. Doctor lives in Storage settings, which users rarely open, so
conflicts (duplicate ids, merge markers, invalid frontmatter) would
otherwise go unnoticed. Safe fixes are excluded since the watcher
applies them silently.

Pass a `doctor=scan` query from the startup conflict sonner and trigger
the scan on mount in Storage, then clear the query. Previously the action
landed on an empty Vault Doctor section that required pressing Scan
manually.

Move vault doctor state (report, decisions, scan/apply) into a shared
module-level composable so the startup health check and the Storage
section reuse a single report instead of scanning twice. When opened
from the startup notice, reuse the existing report (or scan if absent)
and smooth-scroll to the Vault Doctor section.

The default radio border-input (~30% L) nearly matches the card surface
(~27% L) in dark theme, making unselected radios invisible. Use
border-muted-foreground/50 for a readable outline on any surface.

Replace the per-radio border hack with a surface lift: the Needs decision
panel now sits on bg-background (matching its header), so borders and
radios inside read against the elevated surface instead of blending into
the card. Revert the radio border-color override.

Show the scan spinner only if the scan runs longer than 300ms, mirroring
the existing snippet counts loader. Fast scans no longer flash the loader
for a split second. The button stays disabled on the real scanning flag
so repeat clicks are still blocked instantly.

Apply the same delayed-loader pattern to Apply fixes: show the spinner
only if apply runs longer than 300ms. The button stays disabled on the
real applying flag so repeat clicks are blocked instantly.