Show mod downloads and release dates in the launcher MODS panel

The MODS tab now shows each installed mod's total GitHub downloads
(summed asset download_count across all releases), its first and latest
release dates, and a Sort row (Name / Popularity / Release date /
Last updated) persisted in options.modSort.

The launcher already fetched per-repo release lists for update checks, so
the data rides the same cached fetch: parseRelease keeps download_count
and published_at, writeCache persists them, and a cache entry written
before the fields existed is treated as stale and refetched once instead
of hiding the line behind an old cache.

src/mods/ModUpdate.lua

@@ -102,7 +102,9 @@ function ModUpdate.previewLine(text, maxChars)
   return s
 end
 
--- Decode one GitHub release object into { version, tag, zip, prerelease, body }.
+-- Decode one GitHub release object into { version, tag, zip, prerelease,
+-- name, body, downloads }. `downloads` is the sum of every asset's
+-- download_count, GitHub's own measure of a release's downloads.
 function ModUpdate.parseRelease(doc, modId)
   if type(doc) ~= "table" or not doc.tag_name then
     return nil, "no tag_name in release"
@@ -114,6 +116,13 @@ function ModUpdate.parseRelease(doc, modId)
   local triple = version:match("^(%d+%.%d+%.%d+)")
   local zip = ModUpdate.pickZipAsset(doc.assets, modId, triple)
   local body = type(doc.body) == "string" and doc.body or ""
+  local downloads = 0
+  if type(doc.assets) == "table" then
+    for _, a in ipairs(doc.assets) do
+      local d = type(a) == "table" and tonumber(a.download_count)
+      if d and d > 0 then downloads = downloads + d end
+    end
+  end
   return {
     version = triple,
     tag = tostring(doc.tag_name),
@@ -121,6 +130,8 @@ function ModUpdate.parseRelease(doc, modId)
     prerelease = doc.prerelease == true,
     name = type(doc.name) == "string" and doc.name or triple,
     body = body,
+    downloads = downloads,
+    published = (doc.published_at or doc.created_at or ""):match("^(%d+%-%d+%-%d+)"),
   }
 end
 
@@ -154,7 +165,7 @@ function ModUpdate.parseReleases(jsonText, modId, Json)
 end
 
 function ModUpdate.apiReleasesUrl(repo)
-  return "https://api.github.com/repos/" .. repo .. "/releases?per_page=30"
+  return "https://api.github.com/repos/" .. repo .. "/releases?per_page=100"
 end
 
 function ModUpdate.apiLatestUrl(repo)
@@ -180,6 +191,52 @@ function ModUpdate.pickBest(releases)
   return releases[1]
 end
 
+-- Sum of per-release download counts.  Returns nil when no release carries
+-- the field (a cache entry written before downloads existed), else
+-- { total = <sum>, releases = <release count> } so a caller can tell a
+-- real "0 downloads" apart from "no data yet".
+function ModUpdate.totalDownloads(releases)
+  if type(releases) ~= "table" or #releases == 0 then return nil end
+  local total, hasData = 0, false
+  for _, rel in ipairs(releases) do
+    local d = type(rel) == "table" and tonumber(rel.downloads)
+    if d then
+      hasData = true
+      total = total + d
+    end
+  end
+  if not hasData then return nil end
+  return { total = total, releases = #releases }
+end
+
+-- First and latest release dates ("YYYY-MM-DD", ISO strings compare in
+-- calendar order).  Returns nil when no release carries a date -- same
+-- "no data yet" rule as totalDownloads.
+function ModUpdate.releaseDates(releases)
+  if type(releases) ~= "table" or #releases == 0 then return nil end
+  local first, latest, has = nil, nil, false
+  for _, rel in ipairs(releases) do
+    local p = type(rel) == "table" and rel.published
+    if type(p) == "string" and p ~= "" then
+      has = true
+      if not first or p < first then first = p end
+      if not latest or p > latest then latest = p end
+    end
+  end
+  if not has then return nil end
+  return { first = first, latest = latest }
+end
+
+-- Thousands-separated count for the launcher ("12,345"), plain for small
+-- numbers.  Never throws; garbage in, "0" out.
+function ModUpdate.formatCount(n)
+  n = tonumber(n)
+  if not n or n ~= n or n < 0 then return "0" end
+  local s = tostring(math.floor(n))
+  s = s:reverse():gsub("(%d%d%d)", "%1,"):reverse()
+  return (s:gsub("^,", ""))
+end
+
 -- ------- cache (options.modUpdateCache[repo])
 
 local function cacheStore()
@@ -210,6 +267,22 @@ function ModUpdate.cacheFresh(entry, now, ttl)
     and (now - entry.checkedAt) < ttl
 end
 
+-- A cache entry written before download counts existed carries no
+-- `downloads` on any release.  It is provably stale -- parseRelease always
+-- sets the field now -- so treat it as expired: the next fetch rewrites
+-- the entry in the current format, one refetch per repo, and the launcher's
+-- download line stops hiding behind an old cache.
+function ModUpdate.cacheUsable(cached)
+  if type(cached) ~= "table" or type(cached.releases) ~= "table" then
+    return false
+  end
+  if #cached.releases == 0 then return true end
+  for _, rel in ipairs(cached.releases) do
+    if tonumber(rel.downloads) then return true end
+  end
+  return false
+end
+
 function ModUpdate.writeCache(repo, releases)
   if type(repo) ~= "string" or repo == "" then return false end
   local ok = pcall(function()
@@ -226,6 +299,8 @@ function ModUpdate.writeCache(repo, releases)
         name = rel.name,
         prerelease = rel.prerelease == true,
         body = type(rel.body) == "string" and rel.body or "",
+        downloads = tonumber(rel.downloads) or 0,
+        published = rel.published,
         zip = rel.zip and {
           name = rel.zip.name,
           url = rel.zip.url,
@@ -280,7 +355,7 @@ function ModUpdate.fetchReleases(repo, modId, opts)
   end
   if not opts.force then
     local cached = ModUpdate.readCache(repo)
-    if ModUpdate.cacheFresh(cached) then
+    if ModUpdate.cacheFresh(cached) and ModUpdate.cacheUsable(cached) then
       return cached.releases, nil, { fromCache = true }
     end
   end