feat(psychometric): recover Driver p.16 T0MEANSstd after positive T0VAR

[seonghobae]

Stacked on #216 (asymCINTstd). Next unique licensed map on this ancestry is footnote-4 standardisation of 2017-era T0MEANS. Do not duplicate #195 CINTstd. TDPREDVARstd is commented out in the 2017-era source and is not recovered. addedTIPREDVARstd is on the parallel #203 stack and is not recovered here.

Driver, Oud, and Voelkle (2017, Table 2, p. 12; p. 16; footnote 4; JSS PDF re-opened 2026-08-24T22:30Z) print standardised matrices with the suffix std when appropriate. Footnote 4 standardises using only the relevant variance, not the total. Table 2 names T0MEANS the latent process means at the first time point T0. The first-occasion relevant variance is free T0VAR p_0, not process-dynamics asymDIFFUSION -q / (2 a), matching Table 3 T0TIPREDEFFECTstd. The 2017-era summary.ctsemFit.R forms unstandardised T0MEANS:

T0MEANS <- OpenMx::mxEval(T0MEANS, mxobj, compute=TRUE)

That source does not form a T0MEANSstd matrix. The scalar map here is the footnote 4 standardisation of that named first-occasion mean: μ_0 / √p_0.

Recovery

• recover_standardised_initial_latent_mean(μ_0, p_0, clock) forms strictly positive p_0 first, then divides μ_0 by √p_0.
• A zero mean is exactly zero.
• A larger positive p_0 yields a smaller |std|.
• Zero p_0 fails closed. Unstandardised T0MEANS is defined for a zero first-occasion variance; standardised T0MEANS is not.
• Non-event clock fails closed.
• Free T0MEANS does not require stable a < 0.

Claim boundary

• Unstandardised T0MEANS is not T0MEANSstd.
• T0VARstd p_0 / p_0 = 1 recovers the same number when μ_0 = √p_0 and remains a distinct named quantity.
• μ_0 / √asymDIFFUSION uses process-dynamics variance and is not this first-occasion map.

Meredith (1993) and Mislevy (1991) remain closed (Unpaywall 2026-08-24T08:02Z: is_oa: false, 0 locations).

Do not merge without an independent APPROVE plus exact-head required-check success. Do not self-approve. Do not request Copilot.

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[seonghobae]

Folded into the consolidation vehicle #231; this draft stays open until the vehicle merges, then closes as superseded-by-consolidation.

[seonghobae]

Superseded by consolidation: this slice's Driver et al. (2017) standardization recovery landed on protected main through the integration vehicles (#231/#232), and its contract coverage is carried by the reconciled suites (multilevel_event_time_recovery_contract, rubin_and_mean_gate_contract) with test-signature repair tracked in #234. The stacked-draft form is retired to keep the delivery queue at review-ready work only; no capability is lost — the exact-head provenance remains in the vehicle PR descriptions and CHANGELOG.