feat: bump title sizes, add font_scale to logo functions, ship SVGs

- Change rel_large default from 16/14 to 20/14 (~1.43x) to match the
  Civilytics editorial design system. Subtitle now renders at 1.0x base
  instead of 0.86x.
- Switch axis.text to rel() sizing so all text elements cascade from the
  root font_size, enabling uniform scaling.
- Add font_scale parameter (default 1.1) to civilytics_logo(),
  add_logo(), and add_logo_ga() — inflates text by ~10% before
  arrangeGrob composition to compensate for viewport shrinkage.
- Ship SVG logo variants (mark, wordmark, pulse) in inst/img/ for
  Quarto/HTML templates.
- Add "Maintaining brand assets" section to README documenting inst/img/
  file inventory and update workflow.
- Document full font size hierarchy in theme_civilytics() roxygen.

R/logo.R

@@ -46,17 +46,27 @@ get_png <- function(filename) {
 #' @param plot a ggplot2 grob
 #' @param logo a logo grob created by make_logo_grob()
 #' @param margin_param a numeric specifying what margin to add or subtract to align the logo
+#' @param font_scale Numeric. Multiplicative scaling factor applied to text
+#'   sizes before composing the plot with the logo. Default `1.1` inflates
+#'   text by ~10 \% to compensate for the viewport shrinkage caused by
+#'   [gridExtra::arrangeGrob()]. Set to `1` to disable.
 #'
 #' @return a grob with a logo attached to it ready to plot
 #' @importFrom ggplot2 theme
 #' @importFrom gridExtra arrangeGrob
 #' @export
-add_logo <- function(plot, logo, margin_param = NULL) {
+add_logo <- function(plot, logo, margin_param = NULL, font_scale = 1.1) {
+  # Inflate text sizes to compensate for arrangeGrob viewport shrinkage.
+  # All theme text elements use rel() sizing, so scaling the root 'text'
+  # element cascades to titles, axis labels, legends, captions, and strips.
+  if (!is.null(font_scale) && font_scale != 1) {
+    base_size <- plot$theme$text$size %||% 14
+    plot <- plot + ggplot2::theme(
+      text = ggplot2::element_text(size = base_size * font_scale)
+    )
+  }
+
   if(has_caption(plot)) {
-    # convert the caption size to a negative number and on the "pt" scale
-    # p1$theme$plot.caption$size * 1.1
-    # Count the number of lines, which is this + 1
-    # For each line, we can add a certain negative space to align the logo
     cap_lines <- measure_caption(plot)
     if (!is.null(margin_param)) {
       plot <- plot + theme(plot.margin = unit(c(7, 7, margin_param, 7), "pt"))
@@ -107,13 +117,15 @@ has_caption <- function(gg) {
   any(names(gg$labels) == "caption")
 }
 
-#' Add a logo to a ggplot2 object
+#' Add a logo to multiple ggplot2 objects
 #'
 #' @param plot_list a list containing ggplot2 objects
 #' @param logo a grob containing the logo created with `make_logo_grob`
 #' @param nrow an integer, default = 1, for the number of rows to align the plots in
 #' @param widths an optional vector the same length as plot_list with the widths for each plot
 #' @param margin_param a number giving the adjustment up or down to help manually align logo and captions
+#' @param font_scale Numeric. Multiplicative scaling factor applied to text
+#'   sizes before composing. Default `1.1`. See [add_logo()] for details.
 #'
 #' @return a grid object
 #' @note The resulting object needs to be drawn to the screen using grid.draw()
@@ -131,7 +143,18 @@ has_caption <- function(gg) {
 #' grid.draw(plot_and_logo)
 #' dev.off()
 #' }
-add_logo_ga <- function(plot_list, logo, nrow = 1, widths = NULL, margin_param = NULL) {
+add_logo_ga <- function(plot_list, logo, nrow = 1, widths = NULL,
+                        margin_param = NULL, font_scale = 1.1) {
+  # Inflate text sizes to compensate for viewport shrinkage
+  if (!is.null(font_scale) && font_scale != 1) {
+    plot_list <- lapply(plot_list, function(p) {
+      base_size <- p$theme$text$size %||% 14
+      p + ggplot2::theme(
+        text = ggplot2::element_text(size = base_size * font_scale)
+      )
+    })
+  }
+
   # Change position of logo depending on if plot has a caption
   if (!is.null(margin_param)) {
     margin <- theme(plot.margin = unit(c(7, 7, margin_param, 7), "pt"))
@@ -224,6 +247,9 @@ make_logo_grob <- function(type = c("wordmark", "mark"),
 #'   [make_logo_grob()].
 #' @param margin_param Numeric or `NULL`. Manual margin adjustment passed to
 #'   [add_logo()].
+#' @param font_scale Numeric. Inflate text sizes by this factor to compensate
+#'   for viewport shrinkage when composing with [gridExtra::arrangeGrob()].
+#'   Default `1.1` (~10 \% inflation). Set to `1` to disable.
 #'
 #' @return A grob (from [gridExtra::arrangeGrob()]) ready to draw with
 #'   [grid::grid.draw()].
@@ -246,12 +272,20 @@ make_logo_grob <- function(type = c("wordmark", "mark"),
 #'   theme_civilytics_dark()) |>
 #'   civilytics_logo(variant = "dark", type = "mark") |>
 #'   grid.draw()
+#'
+#' # Disable font inflation
+#' (ggplot(mpg, aes(displ, hwy)) +
+#'   geom_point() +
+#'   theme_civilytics()) |>
+#'   civilytics_logo(font_scale = 1) |>
+#'   grid.draw()
 #' }
 civilytics_logo <- function(plot,
                             type = c("wordmark", "mark"),
                             variant = c("light", "dark"),
-                            margin_param = NULL) {
+                            margin_param = NULL,
+                            font_scale = 1.1) {
   logo <- make_logo_grob(type = type, variant = variant)
-  add_logo(plot, logo, margin_param = margin_param)
+  add_logo(plot, logo, margin_param = margin_param, font_scale = font_scale)
 }