fix(ts): rewrite unresolved refs in merged namespaces

[kdy1]

Summary

• rewrite unresolved references to exported namespace members when lowering merged namespace blocks
• keep enum/local identifier rewrites intact by only rewriting unresolved names in that fallback path
• add a fixture regression for issue Typescript namespaces lead to ReferenceError #11514

Testing

• cargo test -p swc_ecma_transforms_typescript --test strip -- --ignored issue_11514
• cargo test -p swc_ecma_transforms_typescript (existing env-dependent failure: issue_960_2 requires mocha)
• cargo fmt --all
• cargo clippy -p swc_ecma_transforms_typescript --all-targets -- -D warnings

Fixes #11514

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Latest commit: 9d0068d

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[github-actions]

Binary Sizes

File	Size
swc.linux-x64-gnu.node	28M (28624456 bytes)

Commit: 85042be

[codspeed-hq]

Merging this PR will not alter performance

✅ 184 untouched benchmarks

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_{Comparing kdy1/fix-issue-11514-namespace-referenceerror (9d0068d) with main (b24b8e0)}