Problem: When multiple Matrix accounts start in parallel, they all trigger
dynamic imports simultaneously. The Rust native crypto module
(@matrix-org/matrix-sdk-crypto-nodejs) crashes when loaded in parallel.
Solution: Add import-mutex.ts that caches import promises. Concurrent callers
now await the same promise instead of triggering parallel imports.
Files changed:
- NEW: src/matrix/import-mutex.ts - serializedImport() utility
- src/matrix/client/create-client.ts - use importCryptoNodejs()
- src/matrix/client/config.ts - use importCredentials()