Stabilize Elasticsearch projection index mappings

[louis4li]

Summary

• Add descriptor-driven Elasticsearch projection mapping augmentation for timestamp and stable identifier fields.
• Preserve explicit provider mappings while skipping open protobuf payload fields.
• Update focused tests and provider docs for the new index mapping/rebuild contract.

Test plan

• git diff --check
• dotnet test test/Aevatar.CQRS.Projection.Core.Tests/Aevatar.CQRS.Projection.Core.Tests.csproj --nologo --filter ElasticsearchProjectionDocumentStoreBehaviorTests
• dotnet test test/Aevatar.GAgentService.Tests/Aevatar.GAgentService.Tests.csproj --nologo --filter ServiceProjectionInfrastructureTests
• dotnet test test/Aevatar.Scripting.Core.Tests/Aevatar.Scripting.Core.Tests.csproj --nologo --filter ScriptingProjectWiringTests

Note: mapping changes are not backward-compatible with old Elasticsearch projection indexes; clear or rebuild affected projection indexes.

🤖 Generated with Claude Code

Fixes #533

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 82.31%. Comparing base (12f4ede) to head (aa71229).
⚠️ Report is 3 commits behind head on dev.

@@           Coverage Diff           @@
##              dev     #665   +/-   ##
=======================================
  Coverage   82.30%   82.31%           
=======================================
  Files         932      932           
  Lines       59485    59483    -2     
  Branches     7805     7805           
=======================================
+ Hits        48960    48961    +1     
+ Misses       7162     7161    -1     
+ Partials     3363     3361    -2     

Flag	Coverage Δ
ci	82.31% <100.00%> (+<0.01%)	⬆️

Flags with carried forward coverage won't be shown. Click here to find out more.

Files with missing lines	Coverage Δ
...data/ScriptCatalogEntryDocumentMetadataProvider.cs	100.00% <ø> (ø)
...etadata/ServiceCatalogReadModelMetadataProvider.cs	100.00% <100.00%> (ø)

... and 2 files with indirect coverage changes

🚀 New features to boost your workflow:

• ❄️ Test Analytics: Detect flaky tests, report on failures, and find test suite problems.
• 📦 JS Bundle Analysis: Save yourself from yourself by tracking and limiting bundle sizes in JS merges.