Workspace skills v2: on-demand skills, long procedures, versions and usage #1148

Follow-up to #1145. Workspace skills are limited today in three ways:

1. Every applied skill of a server is pasted into the MCP initialize instructions, whatever the task. A workspace with a hundred skills sends tens of thousands of characters to the model on every session.
2. A skill is one instruction of at most 2,000 characters. That is enough for a rule, not for a real procedure (a quote workflow, an invoice check), so people keep longer procedures outside AnythingMCP and point to them.
3. There is no history: editing a skill overwrites it, and nobody can tell whether a skill is ever used.

Proposal

• Skills on demand. Two built-in tools on /mcp/:serverId, offered when the caller can see at least one applied skill:
  • skills_list(query?): id, title, when to use, version.
  • skill_get(skill): the full skill (rule + procedure), by id or exact title, limited to skills the caller can see on that server.
• Delivery mode per server (skills_delivery):
  • auto (default): full text while the skills are small (up to about 6,000 characters), otherwise an index of titles and "when to use" plus a pointer to skill_get.
  • inline: always the full text (today's behaviour).
  • index: always the index.
  • Servers whose applied skills are already above the threshold are migrated to inline, so no existing server changes behaviour until an admin picks another mode.
• Long procedures. An optional body (markdown, up to 20,000 characters) next to the short instruction. It is never pasted into the instructions; skill_get returns it. The Skills Finder can file the condensed procedure there.
• MCP prompts. Each applied skill is also offered as an MCP prompt, so clients that support prompts can start it by hand.
• Versions and usage. Editing a skill keeps the previous version (kg_skill_versions) and increments version. skill_get counts uses (use_count, last_used_at). The AI Skills page shows version, usage and history.

The shared /mcp endpoint keeps its fixed toolset; its workspace guide still returns the skills as text.

Migration

New nullable/defaulted columns on kg_skill_suggestions (body, version, use_count, last_used_at) and mcp_server_configs (skills_delivery), a new kg_skill_versions table, and a data update that sets inline on the servers described above. Nothing is removed.