test(apple): share snapshot classification conformance cases across producers #4052

Parent: #4045

Purpose

Bridge trait-based tab/text-input/focused/selected classification is repeatedly aligned to XCTest. Existing bridge tests alone do not independently establish cross-producer semantic parity; collapsed-tab geometry already demonstrates shared-fixture use.

Owner and scope

Shared fixture owner plus packages/platform-apple/src/snapshot-source/tree tests and provider-limrun trait classification/adaptation tests. Swift runner participates only if an existing pure function already consumes equivalent fixture semantics.

Required behavior

Add bounded independent expected classification/state cases for the AX bridge and Limrun, which classify from traits. Identify supported producer inputs and mark unsupported/non-applicable rows. XCTest gets element types from XCUIElement; mark trait-classification rows runner:not-applicable and retain live conformance as the authority for XCTest semantics. Only reuse or extend an existing pure Swift fixture consumer where its semantics actually apply. No test-only production exports, synthetic XCTest parity or new conformance framework.

API or evidence example

Corpus rows may have producer-specific raw inputs plus independent normalized expected role/state; they must not compute expected results with the tested implementation.

Observable completion

• Shared independent expected cases cover recent tab/text-entry semantics plus nearest negatives at actual trait-based producer seams.
• Every row names its applicable backends; XCTest trait classification is not claimed as pure fixture parity.
• No public behavior change, fabricated raw-input equivalence or production test-only seam.
• If a pure Swift function changes, its discovery/build requirements are met; otherwise this task requires no new native build or device lane.

Dependencies and sequencing

Blocked by: none.

Validation

Focused bridge and Limrun TypeScript suites and existing fixture integrity. Native selection/build only if native pure code is touched. Live XCTest semantics stay with existing live conformance; do not substitute fixture results for live evidence.

Base audit SHA: 144bd59890277fd4717995588ad817597c9d6552. Re-read the issue and all Decision: comments before work. Read applicable AGENTS.md routes. Keep one owner boundary per PR. Independent review and serialized exact-head validation are coordinated by the umbrella orchestrator.