Two new SDK control-protocol request types: get_usage and reload_output_styles

The SDK/agent control protocol gains two new request subtypes. get_usage returns the structured /usage data — session cost/usage totals plus claude.ai plan rate-limit utilization — and accepts an optional skip_behaviors flag to skip the 7-day transcript scan that produces the behaviors section; it requires an onGetUsage callback to be registered, or it errors. reload_output_styles re-reads output-style directories from disk mid-session (a style file written mid-session was previously invisible until the next session), returns the refreshed style names, and also drops the shared markdown-file scan cache used by agents, skills, and routines; it's exposed via a corresponding sdk_reload_output_styles wrapper.