feat(serve): complete action registry with all Discord operations

Replaces the if/else dispatch chain with a clean dict-based action
registry. Adds 15 new actions covering the full Discord API surface:

Messages: message_list, message_get, message_search, message_pin/unpin
Channels: channel_list, channel_create, channel_info
Threads: thread_list (added to existing thread_create/thread_send)
DMs: dm_send
Members: member_list, member_info
Roles: role_list, role_assign, role_remove
Server: server_list, server_info

Total: 30 actions available through the serve JSONL protocol.

Bumps to v0.6.0 (minor version for new API surface).

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

Author: DevRohit06

pyproject.toml

@@ -4,7 +4,7 @@ build-backend = "setuptools.build_meta"
 
 [project]
 name = "discord-cli-agent"
-version = "0.5.5"
+version = "0.6.0"
 description = "Discord CLI for AI agents"
 readme = "README.md"
 license = "MIT"