feat(ios-qa): add XCUITest execution-plan module

Standalone planner that turns the IOSQAFlow JSON contract into an
xcodebuild XCUITest invocation for simulator or physical device, using
semantic selectors (identifier/role/label) and no coordinate taps.
Pure plan generation; covered by 7 unit tests.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

ios-qa/executor/README.md

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+# XCUITest execution contract
+
+This directory separates a logical iOS QA flow from where it runs. The same
+semantic flow is routed to an iOS Simulator or a provisioned physical device.
+It emits an `xcodebuild` argv specification; it does not invoke a shell, alter
+signing, or provision a phone.
+
+The checked-in XCUITest runner consumes inline base64 JSON from
+`GSTACK_IOS_QA_FLOW_JSON_BASE64` on physical devices, because a device test
+runner cannot open a path on the Mac. Simulator runs may also consume
+`GSTACK_IOS_QA_FLOW_PATH`. It resolves each selector in
+`selectorCandidates()` order, waits for hittability, performs the action, and
+evaluates the optional post-action verification. A runner must return a
+blocked/unsupported step result rather than falling back to screen coordinates.
+
+Generate a plan:
+
+```bash
+bun ios-qa/executor/cli.ts flow.json target.json runner.json
+```
+
+The JSON result is either `ready` with an argument-safe `xcodebuild` command,
+`blocked` with remediation, or `unsupported` with the offending step id.