fix(loro.js): use Rust's L{lamport}@{peer} format for movable-list JSON element IDs

[zxch3n]

Summary

Found while porting the Rust #1125 MovableList tests to loro.js: their forged JSON updates ("elem_id": "L1@0") could not be imported.

JSON updates that contain MovableList move/set ops are not interoperable between loro.js and Rust/loro-crdt:

• Rust writes elem_id as IdLp, which is L{lamport}@{peer} (crates/loro-common/src/id.rs).
• loro.js wrote {lamport}@{peer}. Rust rejects that with DecodeError("Invalid ID format").
• loro.js fails on Rust's form with counter is out of range: NaN. The Rust fixture loro-js/tests/fixtures/rust/updates.json already contained such ops but was not imported by any test.

Fix

exportJsonUpdates now writes L{lamport}@{peer}. importJsonUpdates accepts it and still accepts the unprefixed form that loro.js 0.2.1 and earlier wrote. The elem_id field type changes from JsonOpID to a new exported JsonIdLp.

Validation

• New test in loro-js/tests/runtime.test.ts: it imports Rust's updates.json, checks it against the same history from updates.blob, and asserts every exported elem_id matches ^L\d+@\d+$. It also checks that the legacy unprefixed JSON still imports. The test fails on main with counter is out of range: NaN. Binary values are normalized in the comparison because the JSON schema stores them as number arrays, and Rust's own JSON round trip does the same.
• Cross-runtime check: Rust main imports loro.js JSON (move + set) and reaches the same value, {"l":["b","B","a"]}. Before this change it failed to decode.
• pnpm --dir loro-js test (17 files, 241 tests), typecheck, lint, format:check all pass.
• No performance impact: this only changes a string prefix on JSON export and import.

Related: #1125, whose tests use this format.

🤖 Generated with Claude Code

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WASM Size Report

• Original size: 3200.65 KB
• Gzipped size: 1058.59 KB
• Brotli size: 741.14 KB