Function shellCandidates

shellCandidates(
    site: SitePhpDurableObject,
): {
    answerable: boolean;
    how: string;
    reasons: Record<string, number>;
    safe: number;
    unsafe: number;
}
Counts stored pages that are shareable shells, with a histogram of why the rest are not.

cfw_page holds only anonymous GETs, which carry no BigPipe placeholders (BigPipe needs a session), so every row is unsafe and safe is always 0. answerable says so; only harvestShellFor() against an authenticated render gives a real verdict.
Parameters
- site: SitePhpDurableObject
Returns {
    answerable: boolean;
    how: string;
    reasons: Record<string, number>;
    safe: number;
    unsafe: number;
}
- answerable: boolean
  
  always false; see the summary
- how: string
- reasons: Record<string, number>
- safe: number
- unsafe: number
- Defined in src/do/shell.ts:45