engine.aggregate: add per-aggregation filter to the contract — ruled half of #10413 (measure-level filters on the ObjectQL analytics path)

[os-zhuang]

Contract-half card created by the triage seat executing the maintainer's #10413 ruling. Provenance: maintainer, live PM chat 2026-08-21, verbatim 「其他接受」 accepting the triage recommendation for #10413 — option A: "给引擎聚合契约加逐聚合过滤,一次修对所有驱动" (widen the aggregate contract with a per-aggregation filter; correct once, for every driver).

Scope

• @objectstack/objectql: the aggregation entry ({ field, method, alias }) gains an optional per-aggregation filter predicate, honoured by the aggregate execution path.
• packages/spec: the executeAggregate bridge on StrategyContext (named by /api/v1/analytics/query still drops per-measure and dataset-level filter on the ObjectQL path — engine.aggregate receives no filter at all #10413 as the spec-owned seam) widened to carry it.
• Driver semantics: drivers that cannot express conditional aggregation natively must refuse loudly or be covered by a documented lowering — no silent drop (the silent drop is exactly the defect being closed).

Consumer

ObjectQLStrategy in packages/services/service-analytics lowers each measure's filter into the new field — that half stays on #10413 (its phase 2, comment-channel Blocked-by: pointing here). The dataset-level filter merge (#10413 phase 1) does NOT wait on this card.

Discipline

Clause-②: yes — this widens a public contract surface. Dispatch at the contract-review tier per the model-tiering rules; needs:contract-review applies on the PR. Acceptance evidence should include the #10413 reproduction (per-measure stage: 'closed_won' filters reaching engine.aggregate and changing the numbers) plus a refusal/lowering test for a driver without native conditional aggregation.

Refs: #10413 (the decision card and measurements) · #10298 / PR #10411 (the native-SQL half, merged).

[os-elon]

Claim: PM loop round 1 (slot reuse after #10457 collection)
Session: session_01B4h3medzvhB9rpfoja9jcw
Branch: claude/issue-10576-aggregate-per-filter
Worktree: objectstack-issue-10576
Domain: domain:spec (cross-package contract card: spec owns the StrategyContext.executeAggregate seam per the card; objectql execution half rides the same PR by the card's own scope)
File surface: packages/spec/src/contracts/analytics-service.ts (the seam, located at :286 on origin/main at claim time), the objectql aggregation-entry type + aggregate execution path in packages/objectql/src/** with its co-located tests, driver refusal/lowering for drivers without native conditional aggregation, .changeset/. NOT in surface: packages/services/service-analytics (that lowering is #10413 phase 2, Blocked-by: pointing here) and the 12 registry-mock test files engine-lane #10551 is collapsing (stop on breach; explain in the report)
Container & model: M, mode:subagent, model: claude-fable-5 — Clause-② mandate from card content (widens a public contract surface; the card says so explicitly); dispatch-gates at claim time: clause-② suspect surface packages/spec/src/**
Clause-②: yes
Serial constraints cleared: in-flight overlap — spec lane: #10485 (stack.zod.ts family, disjoint), fold(#10526+#10336) (data/object.zod.ts prose, disjoint); cross-lane targeted check — engine-lane #10551 (in flight, claude/issue-10551-registry-mock-factory) is collapsing the 12 ./registry module-mock TEST files in packages/objectql/src/**: FENCE — do not edit those 12 files; if an aggregate test this card needs happens to be among them, stop and report rather than colliding; engine-lane #10462 stopped with zero code (empty branch, no claim on any file). Read-coupling: #10413 phase 2 asserts this card's outcome — its Blocked-by: edge points here by design, no in-flight work on it. H17 index: no hit (contracts/analytics-service.ts is not contracts/metadata-service.ts — checked by exact name).

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