Align Copilot guidance with committed pattern-library analysis

[Copilot]

The repository guidance still reflected an older 679-workflow, 7-archetype analysis instead of the committed 2026-08-31 pattern library. This updates the guidance to match the current manifest/archetype data, including empirical rates, curated archetypes, trigger risks, and anti-patterns.

• Pattern guidance refresh

  • Reframes patterns/manifest.json and patterns/archetypes/*.json as the source of truth.
  • Documents current corpus metadata, 27 user-facing archetypes, hidden custom, and 18 curated count: 0 archetypes.
  • Updates empirical success rates, trigger-risk notes, configuration-profile risks, and recommended defaults.

• Regression coverage

  • Adds a focused Vitest test that verifies Copilot instructions stay aligned with committed pattern metadata.
  • Guards against reintroducing stale scan claims like “679 workflows across 269 repos” or “7 archetypes”.

• Lint cleanup

  • Converts an adjacent generated-prompt string to a template literal without changing prompt content.

• Fixes [deep-research] Pattern library analysis: 25 archetypes, trigger risk data, and anti-patterns #265