Align shadcn's accent token with what shadcn means by it

shadcn uses `bg-accent` for its SUBTLE surfaces — dropdown item hover, command
row selection, ghost and outline button hover, the dialog close affordance. The
brand colour in shadcn is `primary`.

PIG's Tailwind config mapped `accent` to `--accent`, which is the brand. That
inverted the meaning, so every shadcn hover and selection state painted a
full-strength brand block. With the monochrome "pig" palette in dark mode the
brand is near-white, so a selected command row rendered as a white slab against
a near-black sheet. Measured before the change: selected row rgb(250,250,250)
on a rgb(9,9,11) body.

`accent` now aliases `--accent-subtle` and `accent-foreground` aliases
`--accent-fg`, which is what those tokens were created for. The eleven places
where PIG's own components wanted a solid brand fill — filled chips, selected
card borders, progress bars — move to `primary`, which still resolves to
`--accent`. A `brand` alias is added for clarity.

After: selected row rgb(39,39,42) in dark and rgb(244,244,245) in light, both a
subtle tint above the body; the pipeline's active stage chip stays a solid
rgb(250,250,250) fill, unchanged.

Found by opening overlays, which earlier screenshot sweeps never did — every
route had been checked, but a dropdown or a command palette only misbehaves
once it is open. Worth remembering: page-level sweeps do not exercise portals.

Typecheck clean, 135 unit tests and e2e green, CSP hash unchanged, 0px
horizontal overflow across 12 routes at 393px and 1440px.

Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>

apps/web/src/components/GoogleSheetsSource.tsx

@@ -137,7 +137,7 @@ export function GoogleSheetsSource({ onLoaded }: { onLoaded(table: GoogleParsedT
           {files.isLoading ? <Skeleton className="h-40" /> : files.isError ? <ErrorText error={files.error} /> : files.data?.files.length === 0 ? <EmptyState title="No spreadsheets found" description="Try another name or confirm this Google account can see the spreadsheet." /> : (
             <div className="grid gap-2 sm:grid-cols-2">
               {files.data?.files.map((file) => (
-                <button key={file.id} type="button" onClick={() => { setSpreadsheetId(file.id); setSheetId(''); }} className={spreadsheetId === file.id ? 'tap min-w-0 rounded-lg border border-accent bg-accent-subtle p-3 text-left' : 'tap min-w-0 rounded-lg border border-border p-3 text-left hover:bg-surface-2'}>
+                <button key={file.id} type="button" onClick={() => { setSpreadsheetId(file.id); setSheetId(''); }} className={spreadsheetId === file.id ? 'tap min-w-0 rounded-lg border border-primary bg-accent-subtle p-3 text-left' : 'tap min-w-0 rounded-lg border border-border p-3 text-left hover:bg-surface-2'}>
                   <p className="truncate text-sm font-medium">{file.name}</p>
                   <p className="mt-1 text-xs text-muted">{file.modifiedTime ? `Modified ${relativeTime(file.modifiedTime)}` : 'Modified time unavailable'}</p>
                 </button>