TypedArray: remaining prototype methods (fill/copyWithin/reduce/join/indexOf/slice/…) + instanceof

[proggeramlug]

Summary

Follow-up to PR #2499 (which wired TypedArray.prototype map/filter/every/some/forEach/find/findIndex). The remaining %TypedArray%.prototype methods are still unwired or broken, and x instanceof Int32Array is false for any typed array.

Concrete gaps (Perry vs Node)

const a = new Int32Array([1,2,3,4,5]);
a.fill(7);                 // Perry: TypeError "(number).fill is not a function"   Node: [7,7,7,7,7]
a.copyWithin(0,3);         // Perry: "(number).copyWithin is not a function"       Node: [4,5,3,4,5]
a.reverse();               // in-place; Node returns same TA reversed
a.reduce((s,x)=>s+x,0);    // Node 15
a.join("-");               // Node "1-2-3-4-5"
a.indexOf(3);              // Node 2
a.lastIndexOf(3);          // Node 2
a.includes(3);             // Node true
a.slice(1,3);              // Node Int32Array [2,3]   (same-kind TA)
a.subarray(1,3);           // Node Int32Array view [2,3]
a.set([9,9], 1);           // writes 9,9 at offset 1
for (const v of a.keys()) {}    // 0..n-1
for (const v of a.values()) {}  // elements
for (const [i,v] of a.entries()) {}

new Int32Array([1,2,3]) instanceof Int32Array   // Perry: false   Node: true

Where the code lives (pattern is established by PR #2499)

The established pattern: the generic js_array_* helper detects a typed-array receiver via crate::typedarray::lookup_typed_array_kind(arr as usize).is_some() and delegates to a js_typed_array_* impl that reads/writes via load_at/store_at (element-typed).

• crates/perry-runtime/src/typedarray.rs — add js_typed_array_{fill,copy_within,reverse,reduce,reduce_right,join,index_of,last_index_of,includes,slice,subarray,set,keys,values,entries} (mirror the map/filter/find_last impls already there). map/filter/slice/subarray return a same-kind TypedArray.
• crates/perry-runtime/src/array/{concat_reverse.rs (js_array_fill, js_array_reverse), immutable.rs (js_array_copy_within), iter_methods.rs (reduce, join), search.rs (indexOf/lastIndexOf/includes)} — add the lookup_typed_array_kind delegation guard at the top (mirror array/sort.rs lines ~25 and PR fix(runtime): TypedArray map/filter/every/some/forEach/find/findIndex read element-typed storage #2499's guards in iter_methods.rs).
• Lowering routing for fill/copyWithin/reverse: these currently error "(number).fill is not a function" because crates/perry-hir/src/lower/expr_call/local_array_methods.rs does NOT route them to the generic Expr::Array* variants for TA receivers — add them to the typed-array-allowed method match there (the is_typed_array arm around the map/filter block).
• instanceof Int32Array: crates/perry-runtime/src/object/instanceof.rs (js_instanceof / js_instanceof_dynamic) + the codegen class-id map in crates/perry-codegen/src/expr/instance_misc1.rs — add reserved class-ids per TA kind detected via lookup_typed_array_kind.

Acceptance criteria

• All methods above byte-match node --experimental-strip-types for Int32Array AND Float64Array (different element kinds).
• map/filter/slice/subarray return a same-kind TypedArray; x instanceof Int32Array true (and false for the wrong kind / non-TA).
• Regular-array versions of these methods unaffected (the guard only fires for genuine TA pointers).
• scripts/test262_subset.py --dir built-ins/TypedArray --max 300 improves; no regression in built-ins/Array.

Refs: PR #2499 (the pattern to copy), Test262 radar #799.