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-of64.md

@@ -0,0 +1,28 @@
+---
+id: hash-of64
+name: Hash.of64
+category: hash
+kind: namespace-method
+tokens: Hash.of64
+sig: Hash.of64(s) -> long
+tip: The fast default 64-bit string hash.
+order: 6
+ns: Hash
+member: of64
+---
+
+The 64-bit counterpart of <a href="hash-of"><code>Hash.of</code></a>: hashes a string to a <code>long</code> instead of a 32-bit <code>int</code>. Use it when you want far fewer collisions than 32 bits can give — large content-id spaces, asset registries, or network identifiers where two different strings sharing a hash would be a real risk. Currently it is <a href="hash-fnv1a_64"><code>Hash.fnv1a_64</code></a>, FNV-1a over the bytes. Deterministic like every hash here: the same string always gives the same 64-bit value.
+
+Parameters:
+- `s` — the string to hash
+
+```ludic
+program Ids64 {
+  entry {
+    let grass: long = Hash.of64("grass_tile")
+    let water: long = Hash.of64("water_tile")
+    print(grass)
+    print(water)
+  }
+}
+```