feat: group Fusion usage by request

[steipete]

Summary

• give every Fusion invocation an internal compound request identity
• group adviser and synthesizer usage into one expandable dashboard row
• preserve per-call cost, failure, latency, and retained-content detail
• audit pre-fan-out and provider-selection failures without merging caller retries

Verification

• pnpm check
• pnpm build
• pnpm worker:e2e
• pnpm --dir admin test
• git diff --check
• autoreview: clean, no accepted/actionable findings

Notes

• incomplete groups caused by the 100-event retention window are marked partial and never overstate completeness or totals
• Access adviser failures retain the synthesizer identity only for audit ownership; provider authorization remains unchanged

[clawsweeper]

ClawSweeper status: review started.

I am starting a fresh review of this pull request: feat: group Fusion usage by request This is item 1/1 in the current shard. Shard 0/1.

This placeholder means the worker is alive and reading the current context. I will edit this same comment with the actual review when the claws are done clicking.

Crustacean status: shell secured, claws on keyboard, evidence pebbles being sorted.