chore: revise noorm skill to focus exclusively on this repo

[damusix]

The noorm skill (used by Claude Code) needs to be revisited. It currently covers broader patterns that aren't specific to this repo. It should be tightened to focus exclusively on the noorm monorepo — its SDK, CLI, conventions, and patterns.

Areas to review:

• Ensure skill content reflects current SDK API surface (e.g. ctx.tvf(), Tvfs generic, impersonation scope)
• Remove or trim guidance that isn't specific to noorm
• Align with existing CLAUDE.md and .claude/rules/ — avoid duplication
• Cover common SDK patterns: createContext, proc/func/tvf, noorm.* namespaces, worker bridge
• Cover CLI/TUI patterns: headless commands, help system, focus system, observer hooks