feat(ludic.base): the vocabulary mechanic packages share - Tick, phases, Queue<T>, rng streams, the save tree, the system runner

A mechanic package depends on ludic.base and nothing else: ports (records of
function values for now) for questions, queues for facts, verbs for changes,
phases for order and its own versioned save section. The runner inits, resets,
saves and loads systems in the order added and ticks them phase by phase; a
missing save section is a reset. Tests for each piece and a worked route
between two toy mechanics live under tests/. The old ludic.core (engine ECS
components) is used by examples/library and stays.

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

packages/ludic.base/save.ludic

@@ -0,0 +1,47 @@
+# ludic.base/save.ludic - the save is a tree, and each system writes its own section under its
+# own key with its own version: {"fishing": {"v": 3, ...}}. By key, never by position; a missing
+# key is a reset. The member "v" is the section's and a system may not use it.
+export property SaveNode {
+  found: bool = false
+  version: int = 0
+  data: Val = null
+}
+
+export function save_tree() -> Val { return Value.object() }
+
+# writes v (an object, or anything else, which is kept under "data") at root[key]
+export function save_section(root: Val, key: string, version: int, v: Val) -> void {
+  let sec = Value.object()
+  Value.put(sec, "v", Value.int(version))
+  if v == null {
+    Value.put(root, key, sec)
+    return
+  }
+  if Value.kind(v) == 6 {
+    for i in 0 .. Value.count(v) {
+      let k = Value.key_at(v, i)
+      if k != "v" { Value.put(sec, k, Value.at(v, i)) }
+    }
+  } else {
+    Value.put(sec, "data", v)
+  }
+  Value.put(root, key, sec)
+}
+
+# the section at root[key]: found false (and an empty object) when there is none
+export function load_section(root: Val, key: string) -> SaveNode {
+  let n = new SaveNode
+  n.data = Value.object()
+  if root == null { return n }
+  if Value.kind(root) != 6 or Value.has(root, key) == 0 { return n }
+  let sec = Value.get(root, key)
+  if Value.kind(sec) != 6 { return n }
+  n.found = true
+  n.version = sv_int(sec, "v", 0)
+  n.data = sec
+  if Value.count(sec) == 2 and Value.has(sec, "data") != 0 { n.data = Value.get(sec, "data") }
+  return n
+}
+
+export function save_encode(root: Val) -> string { return Json.encode(root) }
+export function save_decode(text: string) -> Val { return Json.parse(text) }