feat(types): Dict + Set string-keyed containers (#54)

Types phase 4 — containers. A splice-on-demand open-addressing hash table
(runtime/native/dict.ludic, FNV-1a, linear probing, tombstones, grow at 0.7)
behind two namespaces:

- Dict.* — string -> int map: new/set/get/get_or/has/remove/size/clear/keys.
  Resource counts, id/name registries. O(1) average vs a linear list scan.
- Set.* — set of strings: new/add/has/remove/size/clear/members. Tags,
  unlocked achievements, visited tiles. Shares the same table.

Values are int (also an entity handle / small id); Value.* covers richer
maps. [T; N] inline fixed arrays remain future work — typed buffers and []T
slices already cover heap-backed arrays.

Wired: parser splice trigger (g_uses_dict), emit_call dispatch, reseeded seed,
a self-asserting example (examples/library/containers.ludic + feat_case), and
per-symbol docs + inventory. All suites green incl. golden renders byte-
identical and the bootstrap fixpoint.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

docs/language/set/set-new.md

@@ -0,0 +1,22 @@
+---
+id: set-new
+name: Set.new
+category: set
+kind: namespace-method
+tokens: Set.new
+sig: Set.new() -> Set
+tip: Create an empty string set.
+order: 0
+ns: Set
+member: new
+---
+
+Creates an empty <code>Set</code> of string members. Add to it with <code>Set.add</code> and test membership with <code>Set.has</code>.
+
+```ludic
+program Demo {
+  handler Step phase Update {
+    let tags = Set.new()
+  }
+}
+```