Provider Hub v0.6.9

Accounting correctness fixes

• Partial usage frames now only update fields they actually contain, preserving token fields captured from earlier frames.
• Null or absent provider cost is not treated as reported zero; route pricing estimation remains available.
• Summary metrics now distinguish client requests from route attempts and failovers.
• One 503 then successful failover counts as one successful request, two attempts, one failed attempt, and one failover.
• Request success/failure and average latency are grouped by Provider Hub request UUID and use end-to-end client request timing.
• Token and cost totals still include every actual route attempt, because failed attempts can consume billable usage.

Verification

• 94/94 tests passed.
• Added partial usage/null-cost regression and request-level failover summary timing tests.
• Package dry-run, syntax and diff checks passed.

SHA-256: C9177B62802590E5EB8E702982EDE6FE3F3EABA620F439CD77F43AC17B8910C6