Show Claude monthly extra-usage spend alongside quota windows #1944

Claude usage currently exposes rolling quota windows but omits supported monthly extra-usage spending budgets, both for managed OAuth reads and CLIProxy reads that reuse the same parser.

Evidence: parseClaudeWindows preserves the 5-hour window but drops both enabled spend {used,limit} money objects and extra_usage {used_credits,monthly_limit} budgets. Isolated fixtures with 4,631/50,000 minor units should represent 9.262% and retain the appropriate currency/exponent; current output only includes the rolling window. This is a helper-level coverage finding, not a live-account observation.

Acceptance criteria:

• Preserve supported monthly spend formats through both direct and proxy response decoding.
• Model monetary spending separately from rolling token/request quotas; keep amount units, currency/exponent, enabled state and unknown reset semantics explicit.
• Validate non-finite/malformed/disabled/zero-limit budgets without inventing percentages or dollars.
• Show monthly spend clearly alongside existing quota windows, respecting selected account/computer identity and stale/error states.
• Exercise both response formats and disabled budgets with synthetic fixtures; no live credentials required.

Tracked by #1926. Coordinate with #1904 for recovery behavior, but do not infer a retry/reset time from a monthly dollar budget.