feat(scripts): add library-decisions trace schema + template

Creates the shared schema module for library evaluation traces
(ADR-022 §4): Zod-validated frontmatter with all 8 filter fields and
enum constraints, plus parseTrace/validateTrace exports and a custom
YAML frontmatter parser for the nested trace format.

Also adds docs/library-decisions/_template.md with all 11 required
headings (8 Filter + 3 Prompt) in machine-checkable ADR-022 order.

Adds zod as a root devDependency so the script is runnable directly
from the workspace root without a package context.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

pnpm-lock.yaml

@@ -43,6 +43,9 @@ importers:
       typescript:
         specifier: ^5.8.0
         version: 5.9.3
+      zod:
+        specifier: ^3.25.0
+        version: 3.25.76
 
   apps/cms:
     dependencies: