perf(crosscheck): reuse the Azure reviewer host

[ruby-dlee]

Summary

• admit exact-head semantic findings from cited code instead of launching proof VMs
• reuse one isolated Azure reviewer host with a unique generation directory and managed run command per review
• retain four FIFO controller lanes, Ketch lookup, one bounded verdict repair, exact-head binding, staged-blob cleanup, and fail-closed validation
• simplify operator docs around the supported wrapper and durable review output

Validation

• bash tests/fm-crosscheck.test.sh
• bash tests/fm-crosscheck-azure.test.sh
• python3 -m unittest tests.test_fm_crosscheck_ledger
• Python, Node, Bash, JSON, and diff syntax checks