feat: Add Feishu WebSocket long connection support

[eathard]

Pull Request: Feishu WebSocket Long Connection Support

Summary

Implements WebSocket long connection mode for Feishu/Lark integration, enabling OpenFang to receive messages from local environments without requiring public IP or port forwarding.

Changes

• Core Implementation: Complete WebSocket protocol support with protobuf encoding/decoding
• Connection Mode: Added FeishuConnectionMode enum (websocket/webhook)
• Protocol: Manual protobuf implementation without external .proto files
• Features:
  • Dynamic ticket-based authentication
  • Ping/pong keepalive mechanism (configurable interval)
  • Message fragmentation handling for large payloads
  • Gzip compression support
• Bug Fixes: Fixed receive_id error by using chat_id instead of sender_id
• Logging: Enhanced visibility with info-level logs for WebSocket operations

Files Modified

• crates/openfang-channels/src/feishu.rs (+998 lines)
• crates/openfang-types/src/config.rs (+22 lines)
• crates/openfang-channels/Cargo.toml (+4 dependencies)
• Cargo.lock (dependency updates)
• crates/openfang-api/src/channel_bridge.rs (minor update)

Dependencies Added

• tokio-tungstenite - WebSocket client
• prost & prost-types - Protobuf encoding
• flate2 - Gzip decompression

Testing

✅ WebSocket connection established successfully
✅ Message reception verified with test messages
✅ Protobuf frame decoding functional
✅ Ping/pong keepalive working (90s interval)
✅ Event payload parsing correct

Configuration Example

[channels.feishu]
app_id = "cli_a922bea3c6785cc8"
app_secret_env = "FEISHU_APP_SECRET"
connection_mode = "websocket"  # New: "websocket" or "webhook"
default_agent = "assistant"

Documentation

• Added FEISHU_WEBSOCKET_README.md with setup instructions
• Updated CHANGELOG.md for v0.3.13
• Created RELEASE_NOTES_v0.3.13.md with detailed release notes

Breaking Changes

⚠️ Constructor change: FeishuAdapter::new() now requires connection_mode instead of webhook_port

Before:

FeishuAdapter::new(app_id, app_secret, webhook_port)

After:

use openfang_types::config::FeishuConnectionMode;
FeishuAdapter::new(app_id, app_secret, FeishuConnectionMode::WebSocket)

Checklist

• Code compiles without errors
• Tested locally with WebSocket connection
• Documentation updated
• CHANGELOG updated
• CI/CD tests passing (to be verified)
• No merge conflicts (to be verified)

Related Issues

Resolves: #S143 (Feishu WebSocket Long Connection Implementation)

Additional Notes

• Debug version tested and working (release build pending due to memory constraints)
• Protocol implementation based on official Feishu documentation
• Ready for code review and testing

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Co-Authored-By: Claude Sonnet 4.6 noreply@anthropic.com

[eathard]

Additional Bug Fix Included

This PR now also includes a critical bug fix for UTF-8 character handling:

Fix: UTF-8 character boundary panic in subprocess_sandbox.rs

• Problem: When shell commands contained multi-byte UTF-8 characters (e.g., Chinese), the logging code would panic with: byte index 100 is not a char boundary; it is inside '统' (bytes 98..101)
• Root Cause: Used byte indexing (&command[..100]) to truncate strings for logging, which is unsafe for multi-byte UTF-8 characters
• Solution: Use char_indices() for safe character-boundary string truncation
• File: crates/openfang-runtime/src/subprocess_sandbox.rs

This fix ensures that OpenFang can safely handle shell commands with international characters, making it more robust for global users.