Open-array copy temp leaked a heap block per call

• Type: bug (codegen / managed-heap) — Track A
• Status: DONE — 2026-06-23 (692db33).
• Owner: — (Track A)
• Opened: 2026-06-23 (follow-up noted while closing the open-array fixes)
• Closed: 2026-06-23

Problem

When a fixed array is passed to a const/value or var/out open-array parameter, the compiler copied it into a heap dynamic-array temp (SetLength + COPY_REC). The temp's slot was re-nil'd per call (to avoid over-releasing borrowed managed handles and to stay recursion-safe), so the previous heap block was orphaned — a leak of ~40-48 bytes PER CALL. A 2M-call loop reached ~78-94 MB RSS.

Fix

Replace the heap dyn-array temp with a frame/BSS-local [len:8][data] byte buffer: store the length at buf[0], copy the fixed array into buf+8, and pass buf+8 (the open-array param reads its length at [data-8] and indexes data). A plain byte buffer is reused at the same call site / private per stack frame, so it auto-frees — no per-call heap allocation (recursion-safe; managed element handles are borrowed bytes, no per-element ARC, correct for the read-only / const borrow and for the var copy-out). Both the const/value path and the var/out path (with its post-call copy-out, now sourced from buf+8) use this.

Result: 2M-call loop RSS 94 MB -> 264 KB. Correctness unchanged (the existing open-array tests + var write-back stay green). Managed-field RECORD elements stay excluded (need per-field ARC).

Verification

test/test_open_array_no_leak.pas (2M const+var calls) in make test, with an RSS guard (fails if Maximum-resident > 10 MB). make test + cross-bootstrap byte-identical; ESP suite (var-param + record results) green.