Fixes NovelAgentService continuing a conversation under the wrong
novel's route, since FindConversationAsync matched by id alone. Then
extends NovelAgentToolset to all 45 tools the stdio MCP server offered
(tag/location CRUD, character relationships, arc-stage beat pinning,
question editing, cross-novel novel listing/creation), tagging each
with whether it needs an explicit novel scope so a later MCP adapter
can inject it. Renames the toolset's 33 existing schemas from
snake_case to camelCase to match .NET/REST convention, since nothing
external consumes them.
Lays the groundwork to serve this same registry over MCP at /mcp and
retire the separate stdio Novelly.Mcp project (docs/plans/api/mcp_http_merge_plan.md).