feat(psychometric): restore Driver p.16 TRAITVARstd trait/trait=1 on main

[seonghobae]

Outcome

Restores the executable Driver, Oud, and Voelkle (2017) p. 16 TRAITVARstd scalar on current main after 0ce16e8 dropped the pre-consolidation code while research notes already named the map (register items 81–82).

Head is independent of #267 asymDIFFUSIONstd (open; do not merge). Lands on protected main c7cf34b after #266 analysis-run status HTTP, #265 T0VARstd, #262 T0MEANSstd, #250 asymCINTstd, and #244 discreteCINTstd.

JSS PDF re-opened 2026-08-26T17:45Z from https://www.jstatsoft.org/index.php/jss/article/download/v077i05/1104. Table 2 (p. 12), footnote 4 (p. 16), and §7.1 (pp. 18–19) were read from that PDF in this cycle.

• Table 2 (p. 12) names TRAITVAR φ_ξ the latent trait variance/covariance and sets it NULL when there is no trait.
• Section 7.1 names traits the stable between-subject differences (unit-level unobserved heterogeneity) and estimates φ_ξ of the intercepts ξ across individuals. Distinct from indicator-level MANIFESTTRAITVAR.
• Page 16 prints standardised matrices with the suffix std when appropriate. The printed example on p. 16 is discreteDRIFTstd, not TRAITVARstd.
• Footnote 4: standardisations use only the relevant variance, not the total. The relevant variance for that named between-subject correlation is TRAITVAR, not free first-occasion T0VAR and not process-dynamics asymDIFFUSION.
• The 2017-era summary.ctsemFit.R forms TRAITVARstd only when TRAITVAR != 0, as solve(sqrt(diag(TRAITVAR))) %&% TRAITVAR when verbose = TRUE. OpenMx %&% is t(A) %*% B %*% A. Unlike T0VARstd, that formation uses diag(diag(TRAITVAR)) and does not add diag(c(ridging)). The ridge is a T0VAR numerical hack and is not this exact map.
• Scalar map: trait / trait = 1 after strictly positive TRAITVAR. Form strictly positive trait first, then 1 / √trait, then (1 / √trait) trait (1 / √trait). Zero TRAITVAR skips forming TRAITVARstd in the 2017-era source and fails closed here. TRAITVAR does not require stable a < 0. A non-event clock fails closed. Distinct positive trait recover the same 1.
• p_0 / p_0 = 1 is T0VARstd and recovers the same number and remains a distinct named quantity. This crate already exports T0VARstd; the refuse names that quantity.
• t0_b² v is addedT0TIPREDVAR and is extra first-occasion TI variance, not this correlation. This crate does not currently export addedT0TIPREDVAR; the refuse still names that quantity.

Still not a Kalman filter, not a matrix expm, not ESEM estimation, not DSEM, not MGCFA, and not ctsem estimation.

Meredith (1993) remains unread (Unpaywall 2026-08-26T17:20Z: is_oa: false; OpenAlex closed; Springer content/pdf is an HTML stub). Mislevy (1991) remains unread on the same terms (DOI 10.1007/bf02294457; Unpaywall is_oa: false). #84 metric still does not license latent means.

Do not merge without independent non-author APPROVE and exact-head required-check success. Author will not self-approve. Org has only collaborator seonghobae. Do not request Copilot.

Next restore after this slice: MANIFESTTRAITVARstd (register items 83–84), independently of #267.

Verification at this head

• cargo +1.98.0 test -p psychometric_core --lib — 180 passed
• cargo +1.98.0 test -p psychometric_core --test multilevel_event_time_recovery_contract --test scientific_claim_boundary_contract standardised_trait_variance — 2 + 1 passed
• cargo +1.98.0 clippy -p psychometric_core --all-targets -- -D warnings
• cargo +1.98.0 fmt -p psychometric_core -- --check
• RUSTDOCFLAGS='-D warnings' cargo +1.98.0 doc -p psychometric_core --no-deps

Contract

• crate: psychometric_core (not a second invariance crate)
• map: recover_standardised_trait_variance
• ADR: 0005

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📥 Commits

Reviewing files that changed from the base of the PR and between c7cf34b and ae90cc5.

📒 Files selected for processing (8)

• CHANGELOG.md
• crates/psychometric_core/src/error.rs
• crates/psychometric_core/src/event_time.rs
• crates/psychometric_core/src/lib.rs
• crates/psychometric_core/tests/multilevel_event_time_recovery_contract.rs
• crates/psychometric_core/tests/scientific_claim_boundary_contract.rs
• docs/adr/0005-posterior-esem-dsem.md
• docs/research/multilevel-event-time-recovery.md

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✅ Devin Review: No Issues Found

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