fix: display latency adjustment info on canned forecasters (#447)

[gregfaletto]

Resolves #447.

Summary

print.canned_epipred() was supposed to surface latency-adjustment information (e.g., Aheads adjusted per column: case_rate=2, death_rate=3) for canned forecasters whose recipe contains a step_adjust_latency. It never actually did, because the gating conditional checked for a top-level pre field on the canned forecaster object — but canned forecasters' top-level fields are predictions, epi_workflow, and metadata. The conditional was always FALSE, and the entire latency-info block was dead code.

The fix replaces the conditional with !is.null(x$epi_workflow$pre$actions$recipe), which correctly tests for a recipe preprocessor on the embedded workflow. The latency-info display now works for all four recipe-based canned forecasters (arx_forecaster, arx_classifier, cdc_baseline_forecaster, flatline_forecaster); climatological_forecaster correctly remains unaffected (it overwrites pre with a mold-only list and has no step_adjust_latency).

Test coverage

The existing snapshot tests in tests/testthat/test-snapshots.R already exercised arx_forecaster with adjust_latency = "extend_lags" (out2) and "extend_ahead" (out3) but never observed the latency line because of the bug. Their snapshots regenerate to include the new lines (one + line each in _snaps/snapshots.md — purely additive). Two supplementary expect_match("adjusted", ...) assertions are added next to those snapshot calls as defensive guards: if a future contributor mechanically snapshot_accepts after an unrelated upstream change drops the "adjusted" line, the explicit assertions still catch the regression.

Bookkeeping

• NEWS.md: new # epipredict 0.2.3 section with one bullet.
• DESCRIPTION: version bumped to 0.2.3.
• .gitignore and .Rbuildignore: 3 lines each adding .workflow/, .plans/, and .claude/ to keep personal tooling directories out of git tracking and out of the package build tarball. Happy to split into a separate PR if you prefer.

Out of scope

The original issue mentions a broader concern about partial-matching vulnerabilities in epi_archive / epi_df list subclasses. Those types live in epiprocess, not epipredict. Within this repo, I confirmed via grep that R/canned-epipred.R:115 was the only x$pre access where x was not a workflow object; the others (R/epi_recipe.R:308, R/extract.R:88, R/model-methods.R:89) all operate on workflow objects where pre is the actual field name. A broader audit belongs as a follow-up epiprocess issue.

Test plan

• devtools::test() — 910 passing, 0 failing, 2 skips. The skips (test-get_test_data.R:47 "NA fill behaves as desired" and :85 "forecast date behaves") are pre-existing on dev, added in commit 09fbfd812 (July 2024) as placeholders during the locf-into-step_adjust_ahead refactor; the underlying get_test_data rework is tracked by PR Get test data rework #463 and issues Bug: get_test_data uses na.omit() on all data table columns, rather than just predictors/outcomes #468 / get_test_data returning NA's if there are NA's in the most recent data #267.
• devtools::check(document = FALSE, vignettes = FALSE) — 0 errors. 1 environmental warning (parsnip binary built under R 4.5.2 vs local R 4.5.0 — won't fire in CI). 2 pre-existing notes on dev (top-level Makefile/pkgdown-watch.R, deep ::: import list).
• lintr::lint_package() — zero new findings on lines added by this PR.
• Manually verified before/after: arx_forecaster with step_adjust_latency now shows the latency-adjustment bullet at the bottom of print() output.