Project File Discovery

Part of #7435 — Multi-Language Hook Support

User Story

As a template consumer, I want azd to automatically find my hook's dependency files (requirements.txt, package.json, etc.) so that dependencies are installed without me configuring anything extra.

Solution Approach

Create pkg/tools/language/project_discovery.go (NEW):

• Implement DiscoverProjectFile(scriptDir, boundaryDir string, fileNames []string) (string, error):
  • Walk up parent directories from scriptDir looking for any file in fileNames.
  • Stop at boundaryDir (inclusive) — never escape the project/service root.
  • Return the directory containing the first match, or empty string if not found.
  • Return error only for filesystem errors, not for "not found".
• Define helper constants:
  • PythonProjectFiles = []string{"requirements.txt", "pyproject.toml"}
  • NodeProjectFiles = []string{"package.json"} (future)
  • DotNetProjectFilePattern = "*.csproj" (future, needs glob)

Create pkg/tools/language/project_discovery_test.go (NEW):

• Use t.TempDir() for isolated filesystem fixtures.
• Table-driven tests (follow pkg/tools/python/python_test.go pattern):
  • Project file at script directory level
  • Project file one level up
  • Project file at boundary directory (root)
  • No project file found → returns empty string
  • Script outside boundary → returns error
  • Both requirements.txt and pyproject.toml present → first match wins per slice order
  • Empty directory tree

Files: pkg/tools/language/project_discovery.go (NEW), pkg/tools/language/project_discovery_test.go (NEW)

Acceptance Criteria

• All unit tests pass
• Discovery respects boundary directory (never walks above it)
• Returns directory path (not file path) — caller decides which file to use
• Works on both Windows and Unix path separators
• scriptDir == boundaryDir edge case handled correctly

References

• Contributes to: Multi-Language Hook Support: Python, JavaScript, TypeScript, .NET #7435