Fix incorrect one-arg Base.hash method

Generated as part of an ecosystem-wide audit for one-arg hash methods.

The `hash(arg::LowerOrUpperIndex)` method only defined a one-arg
`Base.hash`, which means the two-arg fallback `hash(x, h::UInt)`
uses `objectid`-based hashing instead. This can cause correctness
issues (equal objects hashing differently) and performance problems
(excessive invalidation). With Julia 1.13+, the default hash seed
is changing from `zero(UInt)` to a random value, which will make
the one-arg method produce different results on each session.

Fix by converting to a proper two-arg method that chains the seed `h`
through the hash computation.

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

Author: adienes

src/index.jl

@@ -42,14 +42,11 @@ function same_to(old::Upper, letter::Letter)
     return Upper(letter)
 end
 
-function hash(arg::LowerOrUpperIndex)
-    h::UInt = 0
-
+function hash(arg::LowerOrUpperIndex, h::UInt)
+    val::UInt = 0
     if typeof(arg) == Lower
-        h |= 1
+        val |= 1
     end
-
-    h |= arg.letter << 1
-
-    h
+    val |= arg.letter << 1
+    hash(val, h)
 end