Fix Napkin Math display capitalization

Author: profvjreddi

book/quarto/config/shared/base/custom-numbered-blocks.yml

@@ -148,7 +148,8 @@ filter-metadata:
         group: perspective
         prefix: psp     # \ref{psp-…} → "Systems Perspective X.Y"
       callout-notebook:
-        label: "napkin math"
+        label: "Napkin Math"
+        reflabel: "napkin math"
         group: engineers-notebook
         prefix: nbk     # \ref{nbk-…} → "napkin math X.Y"
       callout-theorem:

book/quarto/contents/vol1/frontmatter/_conventions.qmd

@@ -35,7 +35,7 @@ Callout boxes are not decoration. Each type signals a specific kind of content,
 | **Definition**          | Formal definition of a key term, with its significance, distinction from the nearest neighbor concept, and a common pitfall                                  |
 | **Example**             | Historical case or concrete scenario, structured as context, insight, and systems lesson                                                                     |
 | **Systems Perspective** | Analytical observation or mathematical nuance that enriches the surrounding argument                                                                         |
-| **napkin math**         | Worked calculation walked through step by step, with values computed inline from the book's constants; intermediate tables and equations are the math itself |
+| **Napkin Math**         | Worked calculation walked through step by step, with values computed inline from the book's constants; intermediate tables and equations are the math itself |
 | **Checkpoint**          | Self-check questions to verify understanding of the preceding section                                                                                        |
 | **War Story**           | Documented engineering incident with a sourced failure mode, structured as context, failure, consequence, and lesson                                         |
 | **Lighthouse**          | Recurring workloads characterized by a profile (parameters, FLOPs, dominant constraint), used as anchored case studies across multiple chapters              |