feat(agent-sessions): read the gateway's usage buckets and llm-call marker - #1149

Confidence 5/5 · safe to merge
A test-fixture-only edit whose output is provably unchanged; the production code it exercises was reviewed at e5adc02.
_{quality 100/100 · no findings · tests not needed · risk low}

The only change since the last review rebuilds the e2e fixture's modelCall helper with a single Object.fromEntries instead of an object literal with a conditional spread. It produces identical attrs, so it is safe to merge.

• modelCall builds its attr record with one Object.fromEntries over MAPLE_AI_LLM_CALL_ATTR, the non-zero buckets and the cost

_{09f070c · Updated on every push. Reply "won't fix" to dismiss a finding, or mention @maple to ask about one.}