Telegram plugin: MCP channel notifications not delivered to conversation

Bug Description

The Telegram plugin (plugin:telegram@claude-plugins-official) successfully receives inbound messages and sends MCP notifications/channel/message via stdio, but Claude Code does not surface these notifications to the active conversation.

Environment

• Claude Code version: 2.1.81
• Platform: macOS (Darwin 25.3.0)
• Launch command: claude --channels plugin:telegram@claude-plugins-official
• Plugin version: 0.0.1 (from ~/.claude/plugins/cache/claude-plugins-official/telegram/0.0.1)

Steps to Reproduce

1. Configure Telegram plugin with valid bot token and access.json (allowlist policy with authorized user ID)
2. Start Claude Code with claude --channels plugin:telegram@claude-plugins-official
3. Verify outbound works: use reply tool to send a message to Telegram — succeeds
4. Send a message FROM Telegram TO the bot
5. Observe: message never appears in the Claude Code conversation

Evidence

Debug logging added to the plugin's server.ts confirms:

2026-03-22T19:44:57.823Z gate result: deliver for sender=6304339334 text=hello
2026-03-22T19:44:57.830Z notification SENT OK for: hello
2026-03-22T19:46:43.754Z gate result: deliver for sender=6304339334 text=can yuo see this
2026-03-22T19:46:43.761Z notification SENT OK for: can yuo see this

The plugin:

• Receives the Telegram update via long-polling ✅
• Passes the access control gate (allowlist check) ✅
• Sends notifications/channel/message via MCP stdio transport ✅
• Claude Code does NOT surface the notification to the conversation ❌

Additional Context

• The StdioServerTransport in @modelcontextprotocol/sdk writes notifications directly to stdout
• The MCP SDK client silently drops notifications without registered handlers (protocol.js — _onNotification returns early if no handler exists)
• This suggests Claude Code's MCP client may not be registering a handler for notifications/channel/message

Expected Behavior

Inbound Telegram messages should appear in the conversation as <channel source="telegram" ...> blocks, enabling bidirectional communication.

Actual Behavior

Only outbound messaging works. Inbound messages are received by the plugin and sent as MCP notifications but never surface in the conversation.