R CMD check: two standing NOTEs (unused sf import, .data/.env globals)

[NewGraphEnvironment]

If we do it: R CMD check on the package is NOTE-free, so a new NOTE is a signal. If we never do: two standing NOTEs hide the next one, as the five NOTEs from #100 hid each other.

Problem

R CMD check --no-manual --ignore-vignettes on the v0.5.6 tarball, built with the #100 .Rbuildignore change, reports 2 NOTEs (measured 2026-10-01, _R_CHECK_FORCE_SUGGESTS_=false). #100 cleared the other 3. These 2 are not caused by #100, and nothing tracks them:

* checking dependencies in R code ... NOTE
Namespace in Imports field not imported from: 'sf'
* checking R code for possible problems ... NOTE
cd_baseline / cd_compare / cd_plot_comparison / cd_plot_timeseries / cd_summary:
  no visible binding for global variable '.data' (cd_summary also '.env')

• NAMESPACE has no import or importFrom lines at all. Code uses the .data and .env pronouns unqualified, and never imports them from rlang.
• sf is in Imports, but no R code calls it. Outside @examples, the only reference is inherits(aoi, "sf") in R/cd_crop.R:30, which does not need the namespace.

Proposed Solution

• Add @importFrom rlang .data .env to a package-level doc (R/cd-package.R), per the r-package convention.
• Decide where sf belongs. It could move to Suggests: the examples call sf::st_read(), and cd_crop() only checks the class. Or it could stay in Imports with a real import, if an sf input should guarantee sf is loaded for the terra::vect() conversion. Check how cd_crop() turns an sf object into a SpatVector before choosing.
• Re-run R CMD check and confirm 0 NOTEs.

Resolution

Landed in #114. Decided: sf moves to Suggests. cd_crop() hands an sf AOI to terra::vect(), and terra 1.9.50 converts it through methods::as(x, "SpatVector"), which loads sf when it is needed (checked in a session with sf not loaded). Anyone holding an sf object therefore already has sf. The 8 tests that read their AOI with sf::st_read() now skip_if_not_installed("sf"). R CMD check is Status OK, 0 NOTEs. The one change users see: pak::pak("NewGraphEnvironment/cd") no longer installs sf.