chore(skills): add components-build standard and wire into skill chain

[jal-co]

Summary

Adds the components.build specification as a repo-local skill and wires it as the canonical engineering standard that all jalco ui skills build on.

What changed

New skill: .pi/skills/components-build/

The full components.build spec (by Hayden Bleasel and shadcn) distilled into a SKILL.md router + 9 reference files (1,113 lines):

Reference	Pillar
composition.md	Compound components, naming, Context sharing
accessibility.md	Keyboard maps, ARIA, focus, contrast, mobile
types.md	HTML extension, single-element wrapping, exported types
styling.md	cn utility, CVA, class ordering, design tokens
state.md	Controlled/uncontrolled, useControllableState
polymorphism.md	as prop, type-safe generics
as-child.md	Radix Slot, prop merging
data-attributes.md	data-state, data-slot, has-[] patterns
taxonomy.md	Artifact classification heuristics

Skill dependency chain

components-build              ← the standard (what a well-built component looks like)
  ↑
jalco-component-builder       ← the workflow (how jalco ui gets there)
  ↑
jalco-shadcn-registry         ← the registry (every item must meet the standard)
jalco-writing-component-docs  ← docs (independent, format-spec driven)

Updated files

• AGENTS.md — references repo-local components-build as MUST for all component architecture decisions
• jalco-component-builder — adds engineering foundation section, engineering standard checklist, taxonomy classification step
• jalco-shadcn-registry — adds to required reading, requires conformance for all registry items
• Removes all references to old component-engineering global skill