Add optional exact_delta metadata to index_repository responses so benchmark artifacts can distinguish changed, affected, and published exact-delta path counts without scraping logs. Keep the benchmark parser backward-compatible by reading response metadata first and stderr markers for older binaries.
Validation: make -j16 -f Makefile.cbm cbm; make -j16 -f Makefile.cbm build/c/test-runner; CBM_ONLY_SUITE=mcp CBM_ONLY_TEST=tool_index_repository_reports_incremental_containment_reason build/c/test-runner; CBM_ONLY_SUITE=mcp build/c/test-runner; bash scripts/check-source-safety.sh; uv run python -m py_compile scripts/benchmark-incremental-speed.py; MCP telemetry smoke /private/tmp/cbm-pan2-20260703T0353Z-exact-delta-telemetry-smoke.json.
Signed-off-by: Andrew Hundt <ATHundt@gmail.com>