Refresh content reader standing-up instructions

[jmchilton]

Summary

• add @galaxy-foundry/content-reader as the eighth baseline reader/contract capability
• replace the obsolete per-instance corpus-walk and wiki-link-map recipe with one explicit content-reader.ts composition point
• document the ownership split for aliases, frontmatter reads, address precedence, extra targets, and companion exclusion
• update the site-kit boundary for the shared ContentNote frame and TagChips markup while keeping domain furniture local
• require explicit Astro collection exports so a generic loop cannot widen discriminated frontmatter types
• add a deliberately small first-reader-slice checkpoint and a published-package handoff check that rejects surviving local link: resolutions

The rendered overview now points at foundry-lib's content-reader boundary as the canonical package-level detail.

Why

The standing-up checklist predates content-reader@0.2.0 and site-kit@0.8.0. Its old instructions would make a new Foundry rebuild mechanics now shared by the Galaxy Workflow, Statistical Genomics, and TDA Foundries. This refresh keeps the pattern responsible for repository composition while leaving package APIs and release versions canonical in foundry-lib.

Validation

• 22 Vitest tests passed
• wiki-link validation passed over 21 files and 21 targets
• Astro check completed with zero errors
• production build generated and Pagefind-indexed 28 pages
• rendered checklist inspected for the new reader boundary and first-slice checkpoint

Existing unrelated output remains unchanged: one unused-variable Astro hint and the CSS optimizer warning about the Google Fonts @import order.