feat: cog_gov_search + cog_mirror + scope-aware verb behavior

Three pieces:

1. cog_gov_search: name/state/type search over canonical_fips_xwalk
   for resolving human-readable place names into canonical_govids.
   Accepts USPS abbrev ('FL') or FIPS int (12) for state; integer
   0-3 or name ('state','county','city','township') for type. Types
   4/5 emit an explanatory cli message and return an empty tibble
   (v0.1 corpus excludes them). USPS<->FIPS table hardcoded with
   50 states + DC + territories; FIPS 66 = GU (not GA).

2. cog_mirror: downloads manifest-listed files to a local directory
   with SHA-256 idempotency (files with matching hash return status
   'cached'). Supports HTTP and local-path fixture URLs. Round-trip
   test: mirror + re-open against the mirror + query Broward 2020
   returns identical results.

3. Scope-aware verbs: .check_govids_in_scope() helper in session.R
   queries canonical_fips_xwalk for the requested govids, emits a
   cli_inform listing any missing ones, and records the found/missing
   sets under provenance$scope. Wired into cog_spending (and
   transitively into cog_revenue, cog_geographic_rollup,
   cog_peer_compare via their cog_spending calls).

Also: dropped dbplyr from Imports (unused).

Tests: +29 (22 search + 12 mirror - 5 refactored) / 159 total pass.
devtools::check() now clean: 0E / 0W / 0N.

man/cog_gov_search.Rd

@@ -0,0 +1,30 @@
+% Generated by roxygen2: do not edit by hand
+% Please edit documentation in R/search.R
+\name{cog_gov_search}
+\alias{cog_gov_search}
+\title{Search for governments by name, state, and/or type}
+\usage{
+cog_gov_search(pattern = NULL, state = NULL, type = NULL)
+}
+\arguments{
+\item{pattern}{Character regex matched case-insensitively against
+`gov_name`. `NULL` (default) means no name filter.}
+
+\item{state}{Either a 2-letter USPS abbreviation (e.g. `"FL"`), a FIPS
+integer (e.g. `12`), or `NULL`.}
+
+\item{type}{Government type: an integer in `0:3` or one of `"state"`,
+`"county"`, `"city"`, `"township"`. Passing `4`, `5`,
+`"special_district"`, or `"school_district"` emits an explanatory
+message and returns an empty tibble (v0.1 corpus excludes those types).}
+}
+\value{
+Tibble from `canonical_fips_xwalk` sorted by `population_acs`
+  descending (`NULL`s last).
+}
+\description{
+Returns rows from `canonical_fips_xwalk` matching the supplied filters.
+Intended as the entry point users call to resolve a human-readable place
+name into one or more `canonical_govid` values before calling
+[cog_spending()] / [cog_revenue()] / etc.
+}

man/cog_mirror.Rd

@@ -0,0 +1,35 @@
+% Generated by roxygen2: do not edit by hand
+% Please edit documentation in R/mirror.R
+\name{cog_mirror}
+\alias{cog_mirror}
+\title{Mirror the published corpus to a local directory}
+\usage{
+cog_mirror(
+  dest,
+  include = c("long", "metadata", "docs"),
+  overwrite = FALSE,
+  progress = interactive()
+)
+}
+\arguments{
+\item{dest}{Destination directory. Created if missing.}
+
+\item{include}{Subset of `c("long", "metadata", "docs")` controlling
+which manifest sections to mirror.}
+
+\item{overwrite}{If `TRUE`, re-copy even when the local SHA matches.}
+
+\item{progress}{If `TRUE`, show a cli progress bar.}
+}
+\value{
+Invisibly, a tibble of `(path, sha256, size_bytes, status)`
+  rows where `status` is `"downloaded"` or `"cached"`.
+}
+\description{
+Downloads (or copies, for local-path fixture URLs) every file listed in
+the session's `manifest.json` into `dest`, preserving the relative path
+structure. Files already present with a matching SHA-256 hash are
+skipped unless `overwrite = TRUE`. The resulting directory can be
+pointed at via `options(uscogdata.url = paste0(dest, "/"))` for offline
+analysis.
+}