Improve unit tests for `src/cli/build.ts`

[samayer12]

Describe what should be investigated or refactored

While working on #2383, we noticed several E2E failures for code changes that should've been caught at the unit-test level. We can improve the quality of unit tests for src/cli in support of #2304.

This issue tracks test improvements to build.ts.

Additional context

Selected output of npx vitest src/cli --coverage

pepr/src/cli                       |   16.42 |    88.46 |   79.16 |   16.42 |                   
  banner.ts                         |       0 |      100 |     100 |       0 | 4                 
  build.helpers.ts                  |   62.87 |    96.15 |   77.77 |   62.87 | 93-95,172-229     
  build.ts                          |       0 |      100 |     100 |       0 | 4-373             
  deploy.ts                         |       0 |      100 |     100 |       0 | 4-169             
  dev.ts                            |       0 |      100 |     100 |       0 | 4-124             
  kfc.ts                            |       0 |      100 |     100 |       0 | 4-45              
  monitor.ts                        |   44.68 |    72.22 |   57.14 |   44.68 | 25-58,84-115      
  root.ts                           |       0 |      100 |     100 |       0 | 4-12              
  types.ts                          |       0 |        0 |       0 |       0 |                   
  uuid.ts                           |       0 |      100 |     100 |       0 | 5-44              
 pepr/src/cli/crd                   |   78.79 |    77.77 |   86.36 |   78.79 |                   
  create.ts                         |   83.33 |      100 |     100 |   83.33 | 25-35             
  generate.ts                       |   79.91 |    72.22 |   86.66 |   79.91 | ...97-208,211-236 
  index.ts                          |       0 |      100 |     100 |       0 | 5-15              
  messages.ts                       |   92.85 |      100 |      75 |   92.85 | 6                 
 pepr/src/cli/format                |   31.25 |      100 |     100 |   31.25 |                   
  format.helpers.ts                 |     100 |      100 |     100 |     100 |                   
  index.ts                          |       0 |      100 |     100 |       0 | 4-66              
 pepr/src/cli/init                  |   54.74 |    97.22 |   76.92 |   54.74 |                   
  enums.ts                          |     100 |      100 |     100 |     100 |                   
  index.ts                          |       0 |      100 |     100 |       0 | 4-149             
  templates.ts                      |      52 |      100 |       0 |      52 | 54-118            
  utils.ts                          |     100 |      100 |     100 |     100 |                   
  walkthrough.ts                    |   89.78 |    95.45 |      75 |   89.78 | 36-40,44-45,56-64 
 pepr/src/cli/update                |       0 |      100 |     100 |       0 |                   
  index.ts                          |       0 |      100 |     100 |       0 | 4-96              
 pepr/src/fixtures                  |       0 |      100 |     100 |       0 |                   
  loader.ts                         |       0 |      100 |     100 |       0 | 3-28              ```