Port Svelte loader and SSR corpus

Bun compatibility slice

Port js/third_party/svelte/svelte.test.ts at exhaustive corpus position 4064.

Required behavior

• expose svelte/compiler and svelte/server surfaces;
• register .svelte component modules through the fixture loader contract;
• support repeated require/dynamic-import query variants without recompilation failures;
• render the expected Svelte SSR boundary markers and interpolated markup;
• retain causal compile/render operation stacks without exposing component source or private props;
• add focused and permanent behavior/error regression coverage.

Tracked from #66.

Implemented and pushed in 013bc84a4.

Coverage now includes:

• svelte/compiler and svelte/server module surfaces;
• fixture loader registration for .svelte files;
• script let extraction, markup interpolation, callable component modules, and generated server-module code;
• stable query-variant resolution across 1,000 requires and 1,000 dynamic imports;
• Svelte SSR boundary markers and expected rendered markup;
• separate SvelteCompileError/SvelteRenderError codes, operations, filenames/components, causes, and causal stacks;
• component-source and private-props redaction from failures.

Verification:

• focused position 4064: 1 file, 4 passed, 0 failed/todo/unsupported/allowed-empty;
• positions 4063–4064: 2 files, 4 passed, 1 intentional todo, 0 failed/unsupported/allowed-empty;
• permanent gRPC error-stack, SQL adapter-contract, third-party corpus, and 43-case behavior/error diagnostic suites all pass.