feat: add map theme variants and fix dark theme text readability

Add theme_civilytics_map(), theme_civilytics_dark_map(), and
theme_civilytics_slide_map() for choropleths — suppress axes, ticks,
gridlines, and axis labels while preserving titles, captions, and legends.

Fix subtitle, caption, and axis text colors in theme_civilytics_dark()
which were inheriting dark ink_2/ink_3 values meant for light backgrounds,
making them hard to read on navy. Now uses navy_200/navy_300 instead.

man/theme_civilytics_slide_map.Rd

@@ -0,0 +1,76 @@
+% Generated by roxygen2: do not edit by hand
+% Please edit documentation in R/theme.R
+\name{theme_civilytics_slide_map}
+\alias{theme_civilytics_slide_map}
+\title{Slide-friendly map Civilytics ggplot2 theme}
+\usage{
+theme_civilytics_slide_map(
+  font_size = 18,
+  font_family = CV_FONT_SANS,
+  title_family = CV_FONT_DISPLAY,
+  line_size = 0.5,
+  rel_small = 12/14,
+  rel_tiny = 11/14,
+  rel_large = 20/14,
+  ink = unname(civilytics_colors["ink"]),
+  paper = unname(civilytics_colors["paper"]),
+  accent = unname(civilytics_colors["ember_600"]),
+  strip_color = unname(civilytics_colors["paper_2"]),
+  paper_bg = FALSE
+)
+}
+\arguments{
+\item{font_size}{Numeric. Base font size in points. Default `14`.}
+
+\item{font_family}{Character. Font family for body/axis text. Default
+`"Inter"` (loaded via showtext).}
+
+\item{title_family}{Character. Font family for plot titles and strip labels.
+Default `"Libre Franklin"` (loaded via showtext).}
+
+\item{line_size}{Numeric. Base line width. Default `0.5`.}
+
+\item{rel_small}{Numeric. Scale factor for small text relative to
+`font_size`. Default `12/14`.}
+
+\item{rel_tiny}{Numeric. Scale factor for tiny text relative to `font_size`.
+Default `11/14`.}
+
+\item{rel_large}{Numeric. Scale factor for large text (titles) relative to
+`font_size`. Default `20/14` (~1.43x), matching the Civilytics editorial
+design system.}
+
+\item{ink}{Character. Hex code for foreground/text color. Defaults to
+[civilytics_colors]`["ink"]` (`#0E1A2B`).}
+
+\item{paper}{Character. Hex code for background color. Defaults to
+[civilytics_colors]`["paper"]` (`#FAF7F2`).}
+
+\item{accent}{Character. Hex code for accent/highlight color. Defaults to
+[civilytics_colors]`["ember_600"]` (`#C25311`).}
+
+\item{strip_color}{Character. Hex code for facet strip background. Defaults
+to [civilytics_colors]`["paper_2"]` (`#F2EDE4`).}
+
+\item{paper_bg}{Logical. If `TRUE` (default), fill the plot and panel
+backgrounds with the warm `paper` color. Set to `FALSE` for a
+transparent background (useful for slides or overlay on colored
+surfaces).}
+}
+\value{
+A complete ggplot2 [ggplot2::theme()] object.
+}
+\description{
+Variant of [theme_civilytics_slide()] for choropleths and spatial plots
+on slides. Combines the larger base font and transparent background of
+the slide theme with suppressed axes, ticks, and gridlines.
+}
+\examples{
+\dontrun{
+library(ggplot2)
+ggplot(map_data) +
+  geom_sf(aes(fill = value)) +
+  scale_fill_civilytics_c("seq_navy") +
+  theme_civilytics_slide_map()
+}
+}