Add more trace spans to execution critical path

[udpatil]

Describe your changes and provide context

This adds more details tracing spans to better visualize the time spent during execution as part of the critical path.

Testing performed to validate your change

jaeger tracing

[github-actions]

The latest Buf updates on your PR. Results from workflow Buf / buf (pull_request).

Build	Format	Lint	Breaking	Updated (UTC)
✅ passed	✅ passed	✅ passed	✅ passed	Sep 29, 2025, 2:42 PM

[codecov]

Codecov Report

❌ Patch coverage is 12.50000% with 42 lines in your changes missing coverage. Please review.
✅ Project coverage is 57.26%. Comparing base (25bb4a7) to head (9084e42).
⚠️ Report is 2 commits behind head on main.

Files with missing lines	Patch %	Lines
internal/state/execution.go	12.50%	30 Missing and 12 partials ⚠️

❌ Your patch status has failed because the patch coverage (12.50%) is below the target coverage (70.00%). You can increase the patch coverage or adjust the target coverage.

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #323      +/-   ##
==========================================
+ Coverage   57.10%   57.26%   +0.15%     
==========================================
  Files         258      255       -3     
  Lines       34487    33956     -531     
==========================================
- Hits        19695    19445     -250     
+ Misses      13214    12980     -234     
+ Partials     1578     1531      -47     

Files with missing lines	Coverage Δ
internal/state/execution.go	60.09% <12.50%> (-4.38%)	⬇️

... and 16 files with indirect coverage changes

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