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/spending.R

@@ -42,9 +42,9 @@ cog_spending <- function(govid, years, category = NULL,
 .verb_spendrev <- function(verb, view, subtype_col, call,
                            govid, years, category,
                            per_capita, adjust_to_year) {
+  govid <- .coerce_govid_input(govid, arg = "govid")
   .validate_verb_inputs(govid, years, category, per_capita, adjust_to_year)
 
-  govid   <- as.character(govid)
   years   <- as.integer(years)
   if (!is.null(adjust_to_year)) adjust_to_year <- as.integer(adjust_to_year)