fix!: enforce to use string for room-id

[zxch3n]

This PR enforces that roomId in the Loro Syncing Protocol must always be a UTF-8 string, removing the ambiguity and complexity of handling both string and Uint8Array types.

Motivation:
Previously, the RoomId type was defined as string | Uint8Array, leading to redundant conversion logic in various parts of the codebase (e.g., simple-server.ts, client-side message handling) and making the protocol less straightforward to implement.

By standardizing roomId to a UTF-8 string, we simplify the protocol specification, streamline implementation efforts, and reduce potential conversion errors across different language and platform bindings.

[chatgpt-codex-connector]

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[Copilot]

Pull Request Overview

This PR standardizes the roomId field in the Loro Syncing Protocol to always be a UTF-8 string, eliminating the previous ambiguity of supporting both string and Uint8Array types. This simplification removes redundant type conversion logic across the codebase and makes the protocol more straightforward to implement.

• Changed RoomId type from string | Uint8Array to just string
• Updated encoding to use varString instead of conditional varString/varBytes
• Removed all conversion logic (bytesToHex, TextDecoder().decode() calls) throughout the codebase

Reviewed Changes

Copilot reviewed 10 out of 10 changed files in this pull request and generated 2 comments.

Show a summary per file

File	Description
protocol.md	Updated documentation to specify varString for room ID instead of varBytes
packages/loro-protocol/src/protocol.ts	Simplified RoomId type definition to just string
packages/loro-protocol/src/encoding.ts	Changed encode/decode to use varString for room ID and removed conditional type handling
packages/loro-websocket/src/server/simple-server.ts	Removed roomIdToString() helper and bytesToHex import, simplified getRoomKey()
packages/loro-websocket/src/client/index.ts	Removed all TextDecoder().decode() conversions for room ID handling
packages/loro-websocket/test-wrappers/recv-index.ts	Changed from Buffer.from(roomId) to direct string usage
packages/loro-protocol/tests/encoding.test.ts	Updated test fixtures to use string room IDs
packages/loro-protocol/tests/encoding.snap.test.ts	Updated test fixtures to use string room IDs
packages/loro-protocol/tests/snapshots/encoding.snap.test.ts.snap	Updated binary snapshots to reflect UTF-8 string encoding
packages/loro-protocol/README.md	Updated example to use string directly instead of TextEncoder

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