[Infra] Create CI build validation workflows for all languages

## Summary

Create fresh GitHub Actions CI build validation workflows for all 5 languages in the repo. This replaces the stale PR #61 which was closed because its branch referenced old directory names that no longer exist on main.

## Requirements

Create one workflow per language, each validating compilation of all samples for that language:

### Workflows needed:
1. **TypeScript** (\ ypescript-build.yml\): \
osql-vector-search-typescript\, \
osql-create-index-typescript\
2. **.NET** (\dotnet-build.yml\): \
osql-vector-search-dotnet\
3. **Go** (\go-build.yml\): \
osql-vector-search-go\
4. **Java** (\java-build.yml\): \
osql-vector-search-java\ — **this was missing from PR #61**
5. **Python** (\python-build.yml\): \
osql-vector-search-python\

### Each workflow must:
- Trigger on push to main + PRs, with path filters for that language's file types
- Include \workflow_dispatch\ for manual runs
- Use \permissions: contents: read\ (least privilege)
- Use \ail-fast: true\ in the matrix strategy
- Use latest stable action versions (v4/v5)
- **Add dependency caching** (\cache:\ parameter on setup actions)
- Reference current \
osql-*\ directory names (NOT the old \mongo-vcore-*\ names)

### Background
- Original issue: #50
- Closed PR: #61 (stale branch, merge conflicts, wrong directory names, missing Java)