Recycle temporary expression scopes on success and failure - #39

Temporary scopes for comparisons and attribute/index updates inherited the surrounding frame's capture marker. A closure holding the parent therefore prevented unrelated temporary copies from returning to the frame pool. Exceptions could also bypass cleanup entirely. Repeated expressions eventually exhausted the CI memory budget.

Clear inherited capture identity on detached copies, retain and register genuine captures, and use a shared cleanup path on both normal return and failure. Add a workload that checks values, closure lifetime and original exceptions, plus a macOS/Linux CI check that verifies frame allocations remain bounded as the iteration count grows.

Validation:

• At 100 and 10,000 iterations, fresh frame counts fell from 602 / 60,002 to 3 / 3. The regression passes with hash indexing ON and OFF.
• The unchanged TestHashOnly#test_broken_hash_value exceeded the 2 GiB limit on main e45622a; the fix passes both assertions in 31.9 seconds with 269,344 KiB peak process-family RSS.
• All 522 corpus programs match Ruby with hash indexing ON and OFF. The new bounded-allocation check also passes on Linux at O2.
• The full Hash file now completes: 306 tests, 1,902 assertions, 0 failures, 1 existing timeout error and 8 skips, at 714,544 KiB peak RSS. The isolated test_replace_memory_leak timeout also reproduces on main; this is not a claim of full Hash compatibility.
• The CI Hash shard also completes all 306 tests (297 MATCH, 1 existing timeout, 8 shared skips), at 678,896 KiB peak process-family RSS. Other CI shards are still running or queued. This PR remains draft pending the final checks.