v0.8 - Langfuse cost tracking, tool-choice benchmark, docs alignment

Rollup over v0.7: Langfuse cost tracking at the router callback (per-tier spend,
fallback events, scores on trace, report CLIs), a fail-closed tier fix (security
stays on Pro on cache miss), a tool-choice benchmark that captures thinking tokens
with the docs corrected to match, a consolidated command reference, four newly
documented scripts and removal of batch-mode framing from the prefix-cache docs.