Spell the project name RainDrop consistently; record the Zenodo DOI

[mrustl]

Reopened after merging the current dev into the branch — the merge conflict that made this PR un-mergeable is resolved.

Spelling

RAINDROP → RainDrop across DESCRIPTION (funder), _pkgdown.yml, roxygen docs and the corresponding man pages, the vignettes, CITATION.cff and .zenodo.json.

Three things deliberately keep their spelling, because they are technical identifiers rather than the project name:

• the engine's fixed output file names (Mulde_Rigole_RAINDROP*.txt, Optimierung_MuldenRigole_RAINDROP*.txt) written by the Tandler engine,
• the strings inside the HDF5 model fixtures (inst/extdata/models/*/base.h5),
• the *_Raindrop_Daten data directories in the local-path examples.

Citation — the concept DOI

CITATION.cff and inst/CITATION now carry the concept DOI 10.5281/zenodo.21839222, which always resolves to the newest release. The placeholder footer pointing to a future DOI is gone.

A version DOI cannot live in the repository: Zenodo mints it only after a release has been archived, so at the moment these files are written — before tagging — the DOI of the release being tagged does not exist yet. Recording the previous release's version DOI instead would make every archived snapshot point at its predecessor. The concept DOI has neither problem: it is fixed from the first release on. Both files carry a comment saying so, so it does not get "corrected" to a version DOI later.

Version DOIs stay available where they are always accurate: the version list on the Zenodo record the concept DOI resolves to.

Two related bits of release-time staleness removed at the same time:

• inst/CITATION takes the package version from meta$Version instead of a hard-coded 0.1.0.
• .zenodo.json deliberately carries no DOI: it describes the upload for which Zenodo mints the next DOI itself.

Conflict resolution against dev

• R/find_min_feasible.R / man/find_min_feasible.Rd — dev replaced the cross-reference to the removed monotonicity_analysis vignette with the external link on raindrop.kompetenz-wasser.io. Resolved in favour of dev's link, with the spelling fix applied to it.
• vignettes/monotonicity_analysis.Rmd — dev deleted it as a deploy-only article (together with vignettes/index.Rmd). The deletion wins over this branch's spelling-only edit.

Carried through to what dev added in the meantime

• _pkgdown.yml — the funder entry that came in with the project logo read RAINDROP, so it no longer matched person("RainDrop", role = "fnd") in DESCRIPTION; pkgdown matches these by name, so the logo would not have been attached to the author. Alt text spelled out as well.
• R/get_simulation_results_all.R, _optim.R, _optim_parallel.R and their man pages — the roxygen titles read "Read Raindrop optimisation simulation results …".

Dropped from the branch

Three man pages that carried only roxygen regeneration noise, no spelling change (dev bumped to roxygen2 8.1.0 after this branch was cut): man/download_engine.Rd and man/run_model.Rd (\link[] anchors resolved against a different R/fs/tools installation) and man/plot_valid_design_space.Rd (indentation only). They now match dev again, so the diff is spelling and citation metadata only.

Verification

R is not available in the environment this was prepared in, so no local R CMD check / devtools::document() run — but the three windows-latest (release/devel/oldrel) R CMD check jobs on this PR exercise inst/CITATION (including meta$Version) and the .Rd cross-references. Checked locally in addition:

• CITATION.cff validates against the official CFF 1.2.0 JSON schema (jsonschema, schema fetched from the citation-file-format repo),
• .zenodo.json parses as JSON, _pkgdown.yml parses as YAML,
• no conflict markers remain, the R/ diff touches roxygen comment lines only, and the pkgdown author key now matches the DESCRIPTION funder name.

What CI does not verify is whether the man pages are bit-identical to what devtools::document() would produce — worth one run on your side before merging.