fix(minifier): preserve unsafe object spreads

[kdy1]

Summary

• Prevent object spread folding from flattening spread sources that are not semantically plain data objects.
• Treat __proto__, computed keys, accessors, impure values, and methods containing super as unsafe spread barriers.
• Add a regression fixture that keeps the frozen "focal_tweet" source literal while preserving computed-property registration behavior.

Test Plan

• git submodule update --init --recursive
• UPDATE=1 cargo test -p swc_ecma_minifier --test compress custom_fixture_tests__fixture__issues__object_spread_frozen_key__input_js -- --ignored
• cargo test -p swc_ecma_minifier --test compress custom_fixture_tests__fixture__issues__object_spread_frozen_key__input_js -- --ignored
• (cd crates/swc_ecma_minifier && ./scripts/exec.sh)
• cargo fmt --all
• cargo clippy --all --all-targets -- -D warnings
• cargo test -p swc_ecma_minifier
• node crates/swc_ecma_minifier/tests/fixture/issues/object-spread-frozen-key/output.js

[changeset-bot]

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Latest commit: a010b5c

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[github-actions]

Binary Sizes

File	Size
swc.linux-x64-gnu.node	27M (27783368 bytes)

Commit: 97452c7

[codspeed-hq]

Merging this PR will not alter performance

✅ 219 untouched benchmarks
⏩ 31 skipped benchmarks¹

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_{Comparing kdy1:kdy1/fix-minifier-object-spread (a010b5c) with main (be38316)}

Footnotes

1. 31 benchmarks were skipped, so the baseline results were used instead. If they were deleted from the codebase, click here and archive them to remove them from the performance reports. ↩