feat(lang,stdlib): 64-bit long type + 64-bit Hash variants (issue #17)

Add `long`, a 64-bit signed integer primitive (i64), threaded through
codegen: llty; int<->long coercion (coerce_code/to_long) at let/assign/
return/call-args; i64 arithmetic + comparison promotion in emit_bin;
unary negate/~; print via %lld and str()/interpolation via @fn_long_str.
Editor vocabulary (syntax header, TextMate grammar, formatter, LSP)
synced; check-vocabulary green. Numeric literals stay i32 — build large
values by widening (documented on the type page).

Complete the Hash.* namespace (issue #17) with both 32- and 64-bit
algorithms: Hash.of/fnv1a/crc32/mix/combine (32-bit) and
Hash.of64/fnv1a_64/mix64 (64-bit, returning long). Deterministic and
C-free; CRC-32 (poly 0xEDB88320) and FNV vectors verified against
reference implementations.

Tests: selfhost/tests/{hash,long}.ludic. Docs: docs/language/hash/*,
type-long.md. Seed reseeded; C-free bootstrap fixpoint holds; 23
selfhost + 45 regression + 29 tooling checks green.

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

docs/language/hash/hash-combine.md

@@ -0,0 +1,30 @@
+---
+id: hash-combine
+name: Hash.combine
+category: hash
+kind: namespace-method
+tokens: Hash.combine
+sig: Hash.combine(...) -> int
+tip: Fold several ints into one deterministic seed.
+order: 5
+ns: Hash
+member: combine
+---
+
+Mixes any number of integers into a single 32-bit value. It folds the arguments left to right with the classic hash-combine step (each value is spread with the golden-ratio constant <code>0x9e3779b9</code> and stirred into the running seed), so the result depends on every input and on their order — <code>Hash.combine(1, 2, 3)</code> and <code>Hash.combine(3, 2, 1)</code> differ. The whole point is a per-thing deterministic seed: hash a world seed with a chunk's coordinates to drive procedural generation, so the same chunk always regenerates identically. Pair it with the noise and random libraries, which take a seed.
+
+Parameters:
+- `...` — the integers to combine (one or more)
+
+```ludic
+program ChunkSeed {
+  entry {
+    let world_seed = 1337
+    let cx = 4
+    let cy = -2
+    let seed = Hash.combine(world_seed, cx, cy)  # this chunk's stable seed
+    print(seed)
+    print(Hash.combine(world_seed, cx, cy) == seed)  # 1 — reproducible
+  }
+}
+```