feat: classify bundled providers by type (MCP servers, LLMs, apps)

[manojbajaj95]

Summary

Introduce a type (or category) field on provider definitions to classify each provider as one of:

Type	Examples
mcp_server	official MCP servers (filesystem, GitHub MCP, Brave search, etc.)
llm	OpenAI, Anthropic, Mistral, Cohere, etc.
app	GitHub (REST), Google, Linear, Okta, Stripe, etc.

Motivation

As the provider list grows (especially after adding official MCP servers — see #360), users need a way to filter, browse, and understand what each provider is. The CLI, any future UI, and agent tooling can use the classification to surface relevant providers contextually (e.g. "show me all LLM providers", "list connected MCP servers").

Proposed Changes

• Add a "type" field to the bundled provider JSON schema (e.g. alongside "name", "auth_flow").
• Classify all existing bundled providers (GitHub → app, Google → app, OpenAI → llm, Okta → app, Linear → app).
• Expose the field via authsome provider list (add a --type filter flag and show the type column in tabular output).
• Validate the field in the provider loader so unknown types surface a clear error.

Work Items

• Update the provider JSON schema to include type (required, enum: mcp_server | llm | app)
• Backfill type on all existing bundled provider JSONs
• Add --type <mcp_server|llm|app> filter to authsome provider list
• Update provider loader validation
• Update docs / README provider table with type column