## Why

The current `config_folders` table provides basic file mounting but lacks structured profile management, ordering, and per-tool-instance selection. We need a proper config profile system that supports ordered includes, mount/file definitions, default selection, and explicit profile assignment per tool instance.

## What Changes

- Add `ConfigProfile` model to replace the legacy `config_folders` concept with structured profiles
- Add `ConfigInclude` model for ordered include lists within profiles
- Add `ConfigMount` model for mount/file definitions (replacing the flat `files` JSONB on `config_folders`)
- Add default profile selection per user and tool type
- Add `selected_profile_id` to `ToolInstance` for per-instance profile selection
- Remove launch-time reliance on legacy active config folder auto-mounting (mark `config_folders.is_active` as deprecated, stop auto-mounting at launch)
- Create database migrations for all new tables
- **BREAKING**: Legacy `config_folders` auto-mounting behavior will be removed; tool instances must explicitly select a profile

## Capabilities

### New Capabilities
- `config-profile-management`: CRUD operations for config profiles, includes, and mounts
- `tool-instance-profile-selection`: Assign and switch config profiles per tool instance

### Modified Capabilities
- `tool-instance-launch`: Change launch behavior to use explicit profile selection instead of auto-mounting active config folder

## Impact

- New database tables: `config_profiles`, `config_includes`, `config_mounts`
- Modified tables: `tool_instances` (add `selected_profile_id`), `users` or `user_configs` (add default profile selection)
- API endpoints for profile management and instance profile assignment
- Tool launch logic changes (remove auto-mount, use explicit profile)