[FEATURE] Per-session spend cap for interactive / auto mode (extend --max-budget-usd beyond -p)

Problem Statement

--max-budget-usd exists but is only available in --print / headless mode.
Semi Interactive sessions — ( auto mode) (--permission-mode auto — have no equivalent safeguard.

Related issues that address adjacent problems (headless cost visibility) but not this one:

• #60921 — background --print spawns burning Max quota
• #57719 — headless orchestrator burned $313 with no cap
• #11008 — expose cost data to hooks (partial workaround)

Proposed Solution

Extend --max-budget-usd (or an equivalent settings.json key, e.g. maxSessionBudgetUSD) to apply in interactive mode, including auto mode