feat: narrow harmonization signposting to per-code gap detection

.build_suggestions() previously flagged a recipe only when the WHOLE
category result had zero rows in a requested year, so a multi-code
category where one recipe component was genuinely gapped never fired
if any sibling code (same recipe or not) had data that year. Each
recipe's own in-category component is now checked individually -- a
component fires when it has no rows in a requested (in-scope) year the
recipe's own generic join otherwise covers, even when the overall
category result looks complete.

Decomposes .build_suggestions() into .category_recipe_components/
.recipe_meta/.component_presence/.recipe_coverage/.recipe_component_gapped
helpers, drops the now-unused `result` param, and rewrites the header
comment to describe the new, deliberately wider scope plus the
per-government `covered` guard that still filters recipes with no data
at all (ordinary reporting variance vs. a real format-boundary gap).

Tests pin the multi-code case the coarse check missed (Cleburne County
FY2012: G05 gapped, G04 covers, masked because E04/E05 have data) next
to the still-guarded no-recipe-coverage case (F04/F05 both absent), and
update the Broward 2019-2020 case to its new, correct expectation (fires
for corrections_combined/corrections_other_capital_combined, still
silent for corrections_capital_combined) plus a fresh true-full-coverage
negative case (Maricopa County).

R/spending.R

@@ -141,7 +141,7 @@ cog_spending <- function(govid, years, category = NULL,
     harmonization <- .build_harmonization_block(
       con, govid, years, resolved, flow_prefixes
     )
-    suggestions <- .build_suggestions(con, govid, years, category, result, resolved$basis)
+    suggestions <- .build_suggestions(con, govid, years, category, resolved$basis)
   }
 
   prov <- .build_provenance(