`checkAuthChallengeSatisfied` answered a `token_expired` challenge with
`isAccessTokenUsable`, which treats "we cannot tell" as "still valid":
`isJwtExpired` returns false whenever the token is not a JWT or carries no
`exp`, and storage never records an absolute expiry (`expires_in` is relative
to an issuance instant that is never persisted).
So for an opaque access token — Doorkeeper, Keycloak in opaque mode,
GitHub-style `gho_…` — the local guess outvoted the resource server's
explicit verdict. Callers short-circuited re-authorization and reconnected
with the same dead credential, looping with no redirect and no ReAuthBanner.
A bare 401 also maps to `token_expired`, so this was not limited to servers
sending `error="invalid_token"`.
Adds `isAccessTokenProvablyUnexpired` beside `isAccessTokenUsable` in
`core/auth/connection-state.ts`: true only for a JWT whose `exp` is still in
the future (same 60s skew). `checkAuthChallengeSatisfied` uses it for the
`token_expired` branch, so absence of local evidence no longer beats the
server, while a provably live JWT keeps its cheap short-circuit.
`isAccessTokenUsable` stays optimistic — it is the right default for
displaying authorization state, and flipping it would show every
opaque-token server as unauthorized.
Closes#2051
Signed-off-by: cliffhall <cliff@futurescale.com>