fix(client/auth): propagate saveTokens errors after refresh

[SAY-5]

Closes #2034

The try { refreshAuthorization(...); saveTokens(...); } catch (error) block in auth() was wide enough to swallow saveTokens() failures (any non-OAuthError, plus ServerError). With rotating refresh tokens, that loses the freshly minted refresh token while the AS has already invalidated the old one, leaving the client unable to recover.

Split the block: the try/catch now wraps only refreshAuthorization, where fall-through to a fresh authorization flow is the intended recovery. saveTokens runs after the catch on a separate, unguarded path so its errors propagate to the caller.

Added a vitest regression test under OAuth Authorization > auth function that mocks saveTokens to reject, asserts the rejection bubbles to the auth() caller, and asserts redirectToAuthorization is never reached. The test fails on main and passes with this change. Full packages/client suite (365 tests) passes; pnpm lint clean.

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