chore(release): v0.12.3 — deduplicate patterns, add schema summaries

- Delete 5 true duplicate patterns (data-chunk, data-duration,
  observability-custom-metrics, observability-tracing-spans,
  leverage-structured-logging) keeping the more comprehensive version
- Rename 4 ambiguous titles in core-concepts (data-cause, data-either,
  data-ref, data-option) to "Understand the X Data Type" form
- Add summary: frontmatter to all 77 schema patterns via new
  scripts/add-missing-summaries.ts
- Update related: references across 12 files to point to kept slugs
- Regenerate README.md (304 patterns, 16 categories, zero empty summaries)

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

Author: PaulJPhilp

README.md

@@ -18,7 +18,7 @@ rule:
     Use Data.array to define arrays whose equality is based on their contents,
     enabling safe, predictable comparisons and functional operations.
 related:
-  - data-chunk
+  - use-chunk-for-high-performance-collections
   - data-struct
   - data-tuple
 author: PaulJPhilp

content/published/patterns/core-concepts/data-array.mdx

@@ -18,7 +18,7 @@ rule:
     Use BigDecimal to represent and compute with decimal numbers that require
     arbitrary precision, such as in finance or scientific domains.
 related:
-  - data-chunk
+  - use-chunk-for-high-performance-collections
   - data-struct
 author: PaulJPhilp
 lessonOrder: 21

content/published/patterns/core-concepts/data-bigdecimal.mdx

@@ -1,5 +1,5 @@
 ---
-title: Handle Unexpected Errors by Inspecting the Cause
+title: Understand the Cause Data Type
 id: data-cause
 skillLevel: advanced
 applicationPatternId: core-concepts

content/published/patterns/core-concepts/data-cause.mdx

@@ -18,7 +18,7 @@ rule:
     Use DateTime to represent and manipulate dates and times in a type-safe,
     immutable, and time-zone-aware way.
 related:
-  - data-duration
+  - representing-time-spans-with-duration
   - data-struct
 author: PaulJPhilp
 lessonOrder: 22

content/published/patterns/core-concepts/data-chunk.mdx

@@ -1,5 +1,5 @@
 ---
-title: Accumulate Multiple Errors with Either
+title: Understand the Either Data Type
 id: data-either
 skillLevel: beginner
 applicationPatternId: core-concepts

content/published/patterns/core-concepts/data-datetime.mdx

@@ -18,7 +18,7 @@ rule:
     Use HashSet to represent sets of unique values with efficient, immutable
     operations for membership, union, intersection, and difference.
 related:
-  - data-chunk
+  - use-chunk-for-high-performance-collections
   - data-array
 author: PaulJPhilp
 lessonOrder: 23

content/published/patterns/core-concepts/data-duration.mdx

@@ -1,5 +1,5 @@
 ---
-title: Model Optional Values Safely with Option
+title: Understand the Option Data Type
 id: data-option
 skillLevel: beginner
 applicationPatternId: core-concepts