feat(ludic.update): a Velopack game updating itself, a frame at a time

latest.json asked once and polled (the newest version and its notes, in
a language or English); then Velopack's releases.<os>.json, the plan (the
delta chain when the installed full package is on disk, no delta is
missing and the chain weighs less than the full one; the newest full
package otherwise, named as the feed names it), each package streamed to
the packages folder with its bytes on a bar and an eased pace, its
SHA-256 by Get-FileHash or shasum in a child, Update patch per delta and
Update apply --waitPid. macOS keeps its packages outside the bundle and
names --rootDir and --packageDir; a translocated app is not installed.

Ports with the runtime as every default: UpdateWorld (platform, exe, pid,
now_ms), UpdateNet (get, download, poll, text, received, free),
UpdateProc (spawn, poll, free). Config: feed, app_id, version, root,
packages, mac_packages, scratch. It words nothing: states, UPDATE_ERR_*
codes and numbers, and UPDATE_STARTED / _STOPPED / _APPLYING facts - the
game exits on the last.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

packages/ludic.update/chain.ludic

@@ -0,0 +1,49 @@
+# chain.ludic - the plan made: the files to fetch, in order, and the base the first delta patches
+function update__plan_clear() -> void {
+  update__files = new []string
+  update__sha = new []string
+  update__size = new []int
+  update__delta = new []bool
+  update__ver = new []string
+  update__full = new []string
+  update__total_bytes = 0
+  update__done_bytes = 0
+  update__i = 0
+}
+
+# the plan from a parsed feed; false when there is nothing newer than this version
+export function update_plan(feed: Val) -> bool {
+  update__plan_clear()
+  let as = update__assets(feed)
+  let n = update__newest_full(as)
+  if n < 0 or not update_newer(as[n].ver, update__conf().version) { return false }
+  let newest = as[n]
+  update__target = newest.ver
+  let base = update_packages() + update__sep() + update__full_name(as, update__conf().version)
+  let chain = update__chain(as, newest.ver)
+  var chain_bytes = 0
+  for i in 0 .. len(chain) { chain_bytes += chain[i].size }
+  let whole = len(chain) > 0 and len(chain) == update__fulls_after(as)
+  if Fs.exists(base) and whole and chain_bytes < newest.size {
+    for i in 0 .. len(chain) { update__plan_add(chain[i], update__full_name(as, chain[i].ver)) }
+    update__old = base
+  } else {
+    update__plan_add(newest, newest.file)
+    update__old = ""
+  }
+  return true
+}
+
+# the plan, for a panel or a test
+export function update_package_count() -> int {
+  if update__files == null { return 0 }
+  return len(update__files)
+}
+
+export function update_plan_file(i: int) -> string { return update__files[i] }
+export function update_plan_is_delta(i: int) -> bool { return update__delta[i] }
+export function update_plan_version(i: int) -> string { return update__ver[i] }
+export function update_target() -> string { return update__target }
+export function update_total_bytes() -> int { return update__total_bytes }
+
+function update__path(i: int) -> string { return update_packages() + update__sep() + update__files[i] }