feat: add role management, member tools, voice channels, and channel permissions

[btallman]

Summary

Adds 12 new tools for Discord server management, covering the most commonly needed features for setting up and managing server structure programmatically:

Role management (4 tools):

• discord_list_roles — list all roles with properties (color, position, hoist, member count)
• discord_create_role — create roles with color, hoist, mentionable, and permission flags
• discord_edit_role — modify existing role properties including position
• discord_delete_role — remove a role

Member management (4 tools):

• discord_assign_role — add a role to a member
• discord_remove_role — remove a role from a member
• discord_list_members — list guild members with their roles (paginated)
• discord_get_member — get detailed info for a specific member

Channel enhancements (4 tools + 1 fix):

• discord_create_voice_channel — create voice channels with optional parent category
• discord_set_channel_permissions — set permission overrides on channels/categories for a role or user
• discord_remove_channel_permissions — remove permission overrides
• Add categoryId parameter to existing discord_create_text_channel so channels can be placed under a category at creation time

Infrastructure:

• Adds GuildMembers intent to support member/role operations

All new tools follow the existing patterns (Zod schemas, handleDiscordError, same response format). The categoryId addition to create_text_channel is backward compatible.

Test plan

All 12 tools were tested against a live Discord server:

• list_roles — returns all roles sorted by position
• create_role — creates role with color and hoist
• assign_role — assigns role to member
• get_member — shows assigned role on member
• remove_role — removes role from member
• delete_role — deletes the role
• list_members — lists all members with roles
• create_text_channel with categoryId — channel created under category
• create_voice_channel with categoryId — voice channel created under category
• set_channel_permissions — deny @everyone ViewChannel, allow specific role
• remove_channel_permissions — removes overrides
• All test artifacts cleaned up after testing