fix: avoid treating Feishu file paths as commands (#1654)

Feishu channel classified any slash-prefixed text (including absolute
paths such as /mnt/user-data/...) as a COMMAND, causing them to be
misrouted through the command pipeline instead of the chat pipeline.

Fix by introducing a shared KNOWN_CHANNEL_COMMANDS frozenset in
app/channels/commands.py — the single authoritative source for the set
of supported slash commands.  Both the Feishu inbound parser and the
ChannelManager's unknown-command reply now derive from it, so adding
or removing a command requires only one edit.

Changes:
- app/channels/commands.py (new): defines KNOWN_CHANNEL_COMMANDS
- app/channels/feishu.py: replace local KNOWN_FEISHU_COMMANDS with the
  shared constant; _is_feishu_command() now gates on it
- app/channels/manager.py: import KNOWN_CHANNEL_COMMANDS and use it in
  the unknown-command fallback reply so the displayed list stays in sync
- tests/test_feishu_parser.py: parametrize over every entry in
  KNOWN_CHANNEL_COMMANDS (each must yield msg_type=command) and add
  parametrized chat cases for /unknown, absolute paths, etc.

Made with Cursor

Made-with: Cursor

Co-authored-by: Willem Jiang <willem.jiang@gmail.com>

backend/app/channels/manager.py

@@ -12,6 +12,7 @@ from typing import Any
 
 from langgraph_sdk.errors import ConflictError
 
+from app.channels.commands import KNOWN_CHANNEL_COMMANDS
 from app.channels.message_bus import InboundMessage, InboundMessageType, MessageBus, OutboundMessage, ResolvedAttachment
 from app.channels.store import ChannelStore
 
@@ -735,7 +736,8 @@ class ChannelManager:
                 "/help — Show this help"
             )
         else:
-            reply = f"Unknown command: /{command}. Type /help for available commands."
+            available = " | ".join(sorted(KNOWN_CHANNEL_COMMANDS))
+            reply = f"Unknown command: /{command}. Available commands: {available}"
 
         outbound = OutboundMessage(
             channel_name=msg.channel_name,