fix(warehouse): read the current semconv key wherever we only read the legacy one - #1190

🟢 Confidence 5/5 · safe to merge
The gRPC-only tone gate and its row-level rpc.system.name read are pinned by the new test, and the tone helper is only reached through pickImportantAttributes.
_{quality 100/100 · no findings · tests covered · risk low}

The head commit gates the rpc.response.status_code chip tone on the row's rpc.system.name (legacy rpc.system fallback), so a gRPC-looking value from another RPC system stays neutral. Contained UI-helper change with a test that fails without the gate.

• getChipTone takes an optional rpcSystem and tones rpc.response.status_code only for gRPC
• pickImportantAttributes reads rpc.system.name (or rpc.system) from the row and passes it to every chip

_{0e1ad0e · Updated on every push. Reply "won't fix" to dismiss a finding, or mention @maple-review-bot to ask about one.}