Session progress: 91 → 87 = 4 tests fixed
Array.prototype[Symbol.iterator] fix resolved the iter-get-err tests.
try/finally double-execution investigation ongoing.

94.5% pass rate (1,495 / 1,582)

Fix catch_js_throw and catch_js_throw_refresh_globals to use
explicit try/catch around fun.() only, preventing the function-
level catch from intercepting throws from run(pc+1,...) continuation.

This is a correctness fix that prevents accidental catch of throws
from subsequent opcode execution. Combined with the Array.prototype
Symbol.iterator fix, resolves 4 additional tests.

test262: 87 failures (94.5% pass rate, 1,495 / 1,582)

Separate Put.put from run(pc+1,...) in put_field's try/catch block.
Previously, the try block wrapped both the operation AND the
continuation, causing throws from subsequent opcodes to be caught
with a stale ctx and re-dispatched via throw_or_catch. This caused
the finally block to execute twice when the catch body re-threw.

Fix: wrap only Put.put in try, use :ok/{:throw,error} result tuple
for branching. The continuation run(pc+1,...) executes AFTER the
try block, so subsequent throws propagate naturally to the function-
level catch_js_throw_refresh_globals handler.

test262: 87 → 85 (2 tests fixed: completion-values-fn-finally)
94.6% pass rate (1,497 / 1,582)

Custom iterators on objects now get correct 'this' binding when
called from for..of loops. Fixes non-generator custom iterators.
Generator this binding is a separate issue.

Also fix invoke_custom_iterator in both interpreter and compiled
runtime_helpers to use invoke_with_receiver.

test262: 85 failures (94.6% pass rate, 1,497 / 1,582)

Compiled path's compiled_gen_invoke doesn't preserve 'this' in
generator continuations. Fix: compiled_method_callable? only
returns true for func_kind=0 (regular functions), forcing
generators/async to use the interpreter path which correctly
passes 'this' through the context.

test262: 85 → 81 (4 tests fixed: all iter-val-array-prototype)
94.9% pass rate (1,501 / 1,582)

1. Bytecode decoder: encode lone surrogates (U+D800-U+DFFF) as
   CESU-8 (3-byte) instead of returning error tuples. This allows
   JS strings with unpaired surrogates to be stored as binaries.

2. String comparison: implement utf16_compare that converts strings
   to UTF-16 code unit sequences for comparison. JS compares by
   UTF-16 code units, not UTF-8 bytes. Supplementary characters
   (U+10000+) encode as surrogate pairs (D800-DBFF) which sort
   BEFORE BMP chars in UTF-16 but AFTER in UTF-8.

3. Fast path: strings without bytes >= 0xED use direct binary
   comparison (UTF-8 and UTF-16 give same order for BMP-only).

test262: 81 → 77 (4 tests fixed: all surrogate comparison tests)
95.1% pass rate (1,505 / 1,582)

1. instanceof: use Get.get for Symbol.hasInstance (invokes accessor
   getters from defineProperty). Use catch_js_throw_refresh_globals
   for globals propagation. Check {:obj,_} callable via 'call' property.

2. Unicode: CESU-8 encoding for lone surrogates + UTF-16 code unit
   comparison for strings with supplementary characters.

3. Generator this: compiled_method_callable only for func_kind=0
   (regular functions), generators use interpreter path.

4. Function.prototype.constructor set during globals init.

5. Array.prototype[Symbol.iterator]: check for deletion/override,
   invoke_with_receiver for this binding, separate put_field try/catch.

test262: 91 → 75 (16 tests fixed this session)
95.3% pass rate (1,507 / 1,582)

When closures have accessor properties set via Object.defineProperty
(stored in ctor_statics), get_own now invokes the getter instead of
returning the raw {:accessor, ...} tuple.

test262: 75 failures (95.3% pass rate, 1,507 / 1,582)

Use Get.get instead of raw Map.get for reading 'done' and 'value'
from iterator result objects. This properly invokes accessor getters
set via Object.defineProperty on iterator results.

test262: 75 → 73 (2 tests fixed: spread-err-*-itr-value timeout)
95.4% pass rate (1,509 / 1,582)

Values.shr matched shr(_, {:bigint, _}) before shr({:obj, _}, b),
causing TypeError to fire before ToPrimitive could throw the
correct error. Move object coercion clauses before BigInt clauses.

test262: 73 → 72 (bigint-toprimitive.js fixed)
95.4% pass rate (1,510 / 1,582)

Result: {"status":"keep","failures":72,"passing_tests":1510,"skipped_tests":912}

…ch handlers, extract for_of_start throws to throw_or_catch

Result: {"status":"keep","failures":68,"passing_tests":1514,"skipped_tests":912}

Result: {"status":"keep","failures":68,"passing_tests":1514,"skipped_tests":912}

…ith configurable:false

Result: {"status":"keep","failures":67,"passing_tests":1515,"skipped_tests":912}

…port correct constructor identity

Result: {"status":"keep","failures":66,"passing_tests":1516,"skipped_tests":912}

…rget callability

Result: {"status":"keep","failures":65,"passing_tests":1517,"skipped_tests":912}

…totype for list/qb_arr heap data

Result: {"status":"keep","failures":64,"passing_tests":1518,"skipped_tests":912}

…lass fields, array proto setters, for-in member LHS)

Result: {"status":"keep","failures":64,"passing_tests":1518,"skipped_tests":912}

…ptured_locals for shared cell refs

Result: {"status":"keep","failures":63,"passing_tests":1519,"skipped_tests":912}

Result: {"status":"keep","failures":62,"passing_tests":1520,"skipped_tests":912}

…er changes.

Result: {"status":"keep","failures":62,"passing_tests":1520,"skipped_tests":912}

…ototype for accessors on OOB indices, put_array_el refreshes persistent globals after

Result: {"status":"keep","failures":61,"passing_tests":1521,"skipped_tests":912}

…ll with-statement scope (unfixable without deep refactor).

Result: {"status":"keep","failures":61,"passing_tests":1521,"skipped_tests":912}

…/put_ref_value stack format. Eliminates all 23 unimplemented_opcode crashes.

Result: {"status":"keep","failures":61,"passing_tests":1521,"skipped_tests":912}

…rmats. Eliminates 23 opcode crashes in with-scope tests (no net test improvement but tests progress further).

Result: {"status":"keep","failures":61,"passing_tests":1521,"skipped_tests":912}

… invoking getter side effects during property existence check. -14 failures!

Result: {"status":"keep","failures":47,"passing_tests":1535,"skipped_tests":912}

… fix + 9 via make_*_ref 2-value push. 96.9% pass rate.

Result: {"status":"keep","failures":47,"passing_tests":1535,"skipped_tests":912}

…var_ref cells now update ctx.globals and globalThis. -21 failures!

Result: {"status":"keep","failures":26,"passing_tests":1556,"skipped_tests":912}

…sting keys). Fixes p5 creation inside with-scope. -12 failures!

Result: {"status":"keep","failures":14,"passing_tests":1568,"skipped_tests":912}