P0: reduce physics-test grounding backlog

[neuron7xLab]

Track the next P0 batch after the 2026-05-29 local validator pass. See docs/physics/P0_MIGRATION_BACKLOG.md and reports/P0_LOCAL_EXECUTION_REPORT_2026-05-29.md for measured counts and priority files.

[neuron7xLab]

Progress (PR #1327, squash-merged to main as 647e6ba): grounded a first batch of physics-test witnesses without masking — no xfail/skip/tolerance loosening; one probabilistic pytest.skip in T17 was removed and replaced with the deterministic INV-CB8 abort path.

Validator (.claude/physics/validate_tests.py tests/ --summary) L1 backlog: 2263 → 2236 (−27). Grounding 474 → 482.

Real INV-* groundings (function docstrings + falsifying structure): test_T9_kuramoto_finite_size_sweep (INV-K2), test_T10_ricci_universal_upper_bound (INV-RC1), test_T17_cryptobiosis_exact_zero (INV-CB1/INV-CB8), test_T_dro1_gamma_algebraic (INV-DRO1), test_inv_dro2_risk_scalar (INV-DRO2), test_T18b_second_order_stability_guard (INV-HPC2 rocof guard).

Correct NON_PHYSICS reclassifications (keyword-matched files witnessing no REGISTERED invariant): test_conservation_aliases (deprecated-alias migration contract), test_dimensional_homogeneity (static unit-label bookkeeping), test_kuramoto_candidate_set + test_kuramoto_no_interference (research governance / filesystem isolation), and two audit-scope honesty tests in test_T18b.

Bound to a diff-bound commit-acceptor (physics-grounding-backlog-batch-823) with a committed inverse-probe falsifier.

Remaining backlog and follow-up notes:

• L1 still ≈2236 across the 276 physics-keyword test files.
• Registry/header drift discovered: CLAUDE.md lists INV-CAL*/INV-LY*/INV-KR1..3/INV-TAU*/INV-DET*/INV-PIN* but .claude/physics/INVARIANTS.yaml does NOT contain them. Files like test_T3_noninjectivity / test_T3_lyapunov_calibration cannot be honestly grounded to a registered invariant until the registry is reconciled — they reference IDs the validator treats as L2-invalid. This should be a separate registry-reconciliation task.
• Many remaining keyword-matched files are infra/smoke/schema/config/namespace tests that are NON_PHYSICS candidates, plus the gravity/newton/maxwell metaphor modules which have no registered invariant at all.