Per workspace agent skills

[shatfield4]

Pull Request Type

• ✨ feat (New feature)
• 🐛 fix (Bug fix)
• ♻️ refactor (Code refactoring without changing behavior)
• 💄 style (UI style changes)
• 🔨 chore (Build, CI, maintenance)
• 📝 docs (Documentation updates)

Relevant Issues

resolves #3855

Description

• add nullable agentConfig column on workspaces storing agent skill overrides, null inherits the instance settings
• scope the in-chat tools menu to the current workspace instead of writing instance-wide settings
• add an agent skills section to workspace settings with a reset to defaults action
• apply workspace overrides to built-in skills, sub-skills, imported plugins, agent flows and MCP tools
• keep overrides working mid-session so toggles apply on the agent's next turn
• only store skills that differ from the instance so everything else keeps following instance changes
• add tests for the agentConfig validation and workspace override resolution

Visuals (if applicable)

Additional Information

• Multiuser mode tested
• Translations PR (will be done after review)

Developer Validations

• I ran yarn lint from the root of the repo & committed changes
• Relevant documentation has been updated (if applicable)
• I have tested my code functionality
• Docker build succeeds locally