Adds two agent-facing AI features: a copilot chat panel in the conversation
sidebar and a generate-reply button in the reply box. Both run an agentic
tool-calling loop whose first tool searches the knowledge base.
Snippets are chunked and embedded on save, then searched in memory with
brute-force cosine similarity (no pgvector). Providers are split into completion
and embedding types. Both are OpenAI-compatible and the API key is encrypted at
rest. Admins can also register custom HTTP tools the model can call.
A new admin AI settings page covers provider config, snippets, and tools. The
v2.6.0 migration and schema add the ai_knowledge_base, embeddings, and ai_tools
tables plus the ai_providers type column.