fix: address code review on #27

- The empty state is about an empty library, not a brand-new Reader:
  listView.Fresh becomes EmptyLibrary and moves behind the tab-specific
  branches, so "No favourites yet" is no longer shadowed for a Reader whose
  library happens to be empty. The action key stays put — hiding it was
  never asked for.
- The owner is not a revocable Reader: their row offers no button and
  POST /readers/{owner}/revoke is a 404, so the one row where the control
  would sign out the tapping browser cannot be reached by a hand-rolled
  POST either.
- Modify isolation is asserted in both directions, and the owner's own
  sign-in through the OAuth callback is pinned to the seeded row.
- CUTOVER.md and REDEPLOY.md still grepped API_TOKEN out of .env for their
  smoke tests, which the last commit deleted; both now take the acting
  Reader's derived credential.
- Roster type follows the machine-fact spec (500 10-11px mono, tracked),
  and PRODUCT.md names the Readers panel instead of claiming there is no
  owner surface at all.

PRODUCT.md

@@ -54,7 +54,7 @@ Not a public reading tracker or social app — a private, self-hosted sync layer
 - Mobile is the primary target; desktop is an enhancement, not the design center.
 - Progress data integrity over visual flourish: `updated_at`/list-ordering behavior is a correctness constraint the UI must respect, not decorate over.
 - A leak between Readers fails silently and looks like working software — isolation is asserted from both directions, never inferred from counting one Reader's rows.
-- No roles, no admin console, no org chrome: one owner capability and otherwise every Reader's view is the same.
+- No roles, no org chrome: the owner's Readers panel is one list with one button (revoke someone's sessions), not an admin console, and otherwise every Reader's view is the same.
 - Prefer native platform affordances (system dark/light, native touch targets) over custom widgetry — this is a lean self-hosted tool, not a product to demo.
 
 ## Accessibility & Inclusion