Delete the measured-redundant tests (test audit TA4, #1731)

[tamashi095]

Test audit phase B, PR 4 (TA4). This PR deletes the tests that mutation measurement (batch 1) found redundant, and adds tests for the real gaps among the mutants that no test caught.

Closes #1731. Adds the specs for #1728, #1729 and #1730.

Summary

• 150 tests deleted (6,905 test-fn lines):
  • 137 MEASURED-REDUNDANT;
  • 8 REDUNDANT-IF-PEER-KEPT (the greedy cover keeps 2 of those rows, plus 2 UNIQUE rows);
  • 5 UNIQUE tests, deleted together with the test-only code they guarded. That code has no product caller: conformance PlanarBlock, compare_f32_to_f64 and verify_bit_exact_repeat; the effect-contract and effect-runtime map_normalized family; lane saved_word.
• 71 helpers deleted (2,041 lines). Each one went only after the compiler reported it unused, and no #[allow] was added. 4 test files that had no tests left are deleted, and so is host-web's unused lane dev-dependency.
• Kept or restored: the UNIQUE tests on product code; the THIN, WEAK and NO-COVERAGE tests; the is_dedicated lags #166: dynamic-rack bank members' buffers are not marked dedicated #169 bank-window regression reproducers; the rack constant-activity count claim.
• The 21 mutants that no test caught:
  • 6 change no behaviour and 3 are unreachable;
  • 7 are in dead code, and the code that TA4 did not delete goes to Remove or use the public functions that only tests call #1730;
  • 5 are real gaps. 4 new tests close them, and each new test is red on its mutant: gate-expander subnormal gain word, session-validator stage labels and message lines, and two realtime-policy D7/D8 rows.
  • lane attest_fp_environment cannot be reached without a seam. Test that the fp-environment attestation refuses a bad readback #1729 adds one.
• For the owner (recorded in the spec):
  • Mutation testing cannot see allocation, count or ceiling claims. host-core still counts allocations on the render path of the deleted capi automation tests.
  • The browser side of the hostile-FP live gate (Compose live level values inside the canonical floating-point environment #1709) is deleted. The capi side stays.
  • retained_ceilings.rs covered only native builds, which do not ship. The wasm32 ceilings stay in expected.json.

The test-by-test list with each test's catchers is in the comments on #1731.

Gates (author, final tree)

• All 31 steps of the qualification lint job: PASS.
• cargo test --locked --all-features over the 30 touched packages: 3,257 passed, 0 failed.
• A fresh verifier gave READY WITH FIXES. The fixes are folded in, and the re-check gave READY.

-10.7k / +0.9k lines over 120 files.

🤖 Generated with Claude Code

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