fix: govid input ergonomics + clearer missing-govid message

Two UX fixes surfaced by first real-user use:

1. cog_spending / cog_revenue / cog_geographic_rollup now accept either
   a character vector OR a data.frame with a canonical_govid column
   (e.g. output of cog_gov_search() or cog_find_peers()). Shared
   .coerce_govid_input() helper in session.R. This lets the natural
   pipe work:

     cog_gov_search('MIAMI', state='FL', type='city') |>
       cog_spending(years=2022, category='Police')

   cog_peer_compare already accepted a data.frame for the peer arg;
   behavior there is unchanged.

2. .check_govids_in_scope() message reworded. The old text led with
   'v0.1 covers gov_types 0-3' which falsely implied the missing govids
   were scope-excluded types when the more common real cause is a typo
   or a guessed value. New message leads with typo + pre-2017 PID,
   mentions scope exclusion as one possibility, and points at
   cog_gov_search() as the recovery path.

Tests: 165 pass / 0 fail. check 0E/0W/0N.

R/rollup.R

@@ -26,8 +26,14 @@
 cog_geographic_rollup <- function(govids, category, years,
                                   per_capita = FALSE, adjust_to_year = NULL) {
   call <- match.call()
-  .validate_rollup_govids(govids)
+  .validate_rollup_layers(govids)
 
+  # Accept character vector OR a data.frame with canonical_govid per layer,
+  # so cog_gov_search() output can be piped into one of the layer slots.
+  govids <- lapply(govids, .coerce_govid_input, arg = "govids[[layer]]")
+  if (any(lengths(govids) == 0L)) {
+    cli::cli_abort("Each layer in `govids` must be non-empty after coercion.")
+  }
   layer_names <- names(govids)
   all_govids  <- unlist(govids, use.names = FALSE)
   layer_map   <- tibble::tibble(
@@ -51,7 +57,7 @@ cog_geographic_rollup <- function(govids, category, years,
 }
 
 #' @noRd
-.validate_rollup_govids <- function(govids) {
+.validate_rollup_layers <- function(govids) {
   if (!is.list(govids) || is.data.frame(govids)) {
     cli::cli_abort("`govids` must be a named list.")
   }
@@ -68,9 +74,6 @@ cog_geographic_rollup <- function(govids, category, years,
       "`govids` names must be one of 'state', 'county', 'city'. Got: {bad}."
     )
   }
-  if (any(lengths(govids) == 0L)) {
-    cli::cli_abort("Each layer in `govids` must be non-empty.")
-  }
   invisible(TRUE)
 }