Fix deep-review infra: temp repo missing CMakeLists.txt (local-only)

[chhwang]

Fix deep-review infra: prevent temp repo from omitting CMakeLists.txt

The deep-review setup agent interpreted Case B ("copy 'before' state")
as cherry-picking only changed files, omitting CMakeLists.txt and other
build files from the temp repo. The verify step then failed with a
cryptic CMake error. This caused improve/verify failures in P11 (cycles
67, 69, 71) and P12 (cycle 74).

No ark code changes. Both fixes are to local workflow infrastructure:

1. Prompt fix (setup.md Case B): Clarified to require full-tree copy
   (excluding .git/) for baseline and diff states, matching Case A's
   explicit "copy codebase" instruction.
2. Pre-flight assertion (dev-verify.sh): Added CMakeLists.txt
   existence check before invoking the remote build. Fails fast with a
   clear error naming the root cause.

This PR is empty against microsoft/ark. The fixes were applied directly
to local files. Safe to close without merging.

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 85.70%. Comparing base (02dcf84) to head (870bee3).
⚠️ Report is 2 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #262      +/-   ##
==========================================
+ Coverage   85.48%   85.70%   +0.21%     
==========================================
  Files         129      129              
  Lines        6457     6457              
==========================================
+ Hits         5520     5534      +14     
+ Misses        937      923      -14     

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[chhwang]

Empty against microsoft/ark — the deep-review infra fix (setup full-tree copy + CMakeLists.txt pre-flight) was applied to local workflow files, not repo code. Closing without merging.