Guard Y249, Y338, Y339, and Y340 regressions

[Parker-fi]

Coverage

• Y249 guards complete conditional lookup results when multiple source rows share a numeric match key.
• Y338 opens the restricted grouped grid in Chromium and verifies that its live record query drops the unreadable group, receives every permitted row, and mounts the grid. Public API checks cover a statically unreadable group, conditional masking, and persisted filter/sort on an unreadable field.
• Y339 guards the multi-value filter contract for a one-to-many User lookup.
• Y340 guards a recomputed User lookup across independent rereads.

Every fixture and permission precondition is created by the runners before the checkpoints. Y249 is a narrow sentinel because its report has no confirmed fix commit.

Verification

• Local and GitHub pnpm check pass.
• Y338 passes locally and in GitHub Actions on current develop, including the browser subscription and all API checkpoints.
• Y338 reproduces before its fix because the browser record subscription still carries the unreadable group field.
• Y338 comparison run: 12407c4092 is present/regression; develop (0df82ae7ec) is absent/pass. The comparison has no missing results, harness errors, or gating regressions.
• Prior local comparison evidence for Y339 and Y340 remains unchanged.
• The branch contains no tracked edition override or personal access token.

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