compile: a multi-MB JSON object literal supplied via --define (OpenCode's models.dev snapshot) never finishes codegen — lower large JSON defines through JSON.parse like #8418 #10151

Parent: #10107 (OpenCode v1.18.30). Related: #10101 / PR #10129 (defines), #8418 (JSON imports lowered via JSON.parse of a serialized constant to avoid exactly this).

Problem

scripts/build_opencode.ts injects OpenCode's models.dev snapshot as a build-time define: OPENCODE_MODELS_DEV = <4,623,748-byte JSON object literal> (the same value Bun's define receives). Perry substitutes the literal at its single use site (packages/core/src/models-dev.ts:199) and then lowers a 4.6 MB object literal into IR. The resulting codegen unit never finishes: on perrymaster (16 cores, 61 GB) the full 7,897-module OpenCode compile stalled with one perry-llvm-unit thread at 100 % for 25+ minutes (the progress log went silent at 3,355 staged objects, RSS flat at 22.5 GB) under PERRY_LL_SIZE_OPT=1 PERRY_LL_PREOPT_OPTNONE_INSTRS=8192, so the per-function optnone escape hatch does not cover it (the literal is one expression, not many functions).

Killing the compile and restarting on the same object cache with --define OPENCODE_MODELS_DEV=undefined (everything else identical) went straight past that point (6,444 objects after 20 minutes) — the fallback path fetches models.dev at runtime, which is not what the shipped binary does.

Repro

cd opencode-v1.18.30 && bun install --frozen-lockfile --ignore-scripts
cd /path/to/perry && bun scripts/build_opencode.ts /path/to/opencode-v1.18.30 --prepare-only --os linux --libc glibc
cd /path/to/opencode-v1.18.30/packages/opencode
perry compile src/index.ts --platform bun --output /tmp/oc --asset-module 'opencode-web-ui.gen.ts=../app/dist'   # after `bun run --cwd ../app build`
# stalls in codegen; PERRY_CODEGEN_PROGRESS=1 log stops; one perry-llvm-unit thread stays at 100 %
perry compile ... --define OPENCODE_MODELS_DEV=undefined   # completes

A standalone reproduction: any module reading a defined identifier whose value is a multi-MB JSON object literal (--define 'BIG=<contents of models.dev api.json>', then export const x = typeof BIG === "undefined" ? undefined : BIG).

Expected

A define whose value is a large JSON literal should lower the way #8418 lowers JSON imports: embed the serialized text as a string constant and materialize it with JSON.parse at first use (or lazily), instead of IR-expanding the literal. Thresholds should be by literal size, independent of the function's instruction count, and the object cache key must still include the define value.

Acceptance

• The repro compiles in seconds; the produced object for models-dev.ts is small (the string constant plus a parse call).
• opencode --version from a build with the real snapshot define prints 1.18.30, and the models list matches the embedded snapshot without a network fetch.
• A regression test with a >1 MiB JSON define under crates/perry/tests.