Add get_store_metrics to the Lite MCP ratchet allow-list

[erikdarlingdata]

Nightly-only failure: Lite.Tests.CrossAppMcpToolInventoryPinTests.LiteMissingMcpTools_MatchTheRatchetAllowList — #2070 added the Darling-only get_store_metrics tool (#2068) and its PR lane didn't run Lite tests, so the ratchet first fired on the nightly. The tool is Darling-only by architecture (Lite is single-instance over local DuckDB: no central store, hypertables, or payload dimensions to measure), so the fix is the allow-list entry with that rationale, same style as the Custom Views entries.

🤖 Generated with Claude Code

[claude]

Reviewed. This is a straightforward, correct fix for the nightly ratchet failure.

Verified:

• get_store_metrics is genuinely Darling-only — no matching tool exists anywhere in Lite/Mcp/*.cs, confirming the architectural rationale (no central store/hypertables/payload dims in Lite's single-instance DuckDB model).
• The new allow-list entry matches the exact style/rationale pattern of the existing Custom Views / alert-tuning / onboarding entries (comment explaining why it's architecture-only vs. "not ported yet", then the string).
• LiteMissingMcpTools_MatchTheRatchetAllowList uses SetEquals, so this entry is required for the test to pass now that Store self-metrics: persist per-hypertable size, compression ratio, and dimension-table series for capacity forecasting #2068 added the tool — matches the stated root cause (PR lane for #2068: hourly store self-metrics — per-hypertable size, compression, and dimension series for capacity forecasting #2070 didn't run Lite tests, so the ratchet only fired on nightly).
• No Lite/Darling parity drift introduced — this documents an intentional asymmetry rather than creating one.
• Single-file, test-only change; no production code, no security or performance surface.

No issues found.