ScriptExecutor Interface and ScriptLanguage Type

Part of #7435 — Multi-Language Hook Support

User Story

As a template author, I want azd to understand that my hook script is written in a specific programming language so that it can handle execution appropriately instead of treating everything as a shell script.

Solution Approach

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

• Define ScriptLanguage type (string) with constants: ScriptLanguageUnknown (""), ScriptLanguagePython ("python"), ScriptLanguageJavaScript ("js"), ScriptLanguageTypeScript ("ts"), ScriptLanguageDotNet ("dotnet").
• Define ScriptExecutor interface:
  • Language() ScriptLanguage
  • Prepare(ctx context.Context, scriptPath string) error — runtime check, dependency install, build
  • Execute(ctx context.Context, scriptPath string, options tools.ExecOptions) (exec.RunResult, error)
• Implement GetExecutor(language ScriptLanguage, ...) (ScriptExecutor, error) factory. Accept dependencies via parameters (not global state) — specifically exec.CommandRunner. Phase 1: Python returns real executor; JS/TS/DotNet return ErrUnsupportedLanguage sentinel.
• Implement InferLanguageFromPath(path string) ScriptLanguage mapping .py → Python, .js → JS, .ts → TS, .cs → DotNet, unknown → ScriptLanguageUnknown.

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

• Table-driven tests for InferLanguageFromPath covering all extensions + unknown.
• Tests for GetExecutor returning real executor for Python, ErrUnsupportedLanguage for others.

Files: pkg/tools/language/executor.go (NEW), pkg/tools/language/executor_test.go (NEW)

Acceptance Criteria

• Package compiles with go build ./pkg/tools/language/...
• InferLanguageFromPath correctly maps .py, .js, .ts, .cs, and unknown extensions
• GetExecutor returns ErrUnsupportedLanguage for JS, TS, DotNet in Phase 1
• ScriptExecutor interface is compatible with tools.ExecOptions from pkg/tools/script.go
• All unit tests pass

References

• Refs: Extends [Issue/enhancement] Cross-platform shell commands behavior #3613
• Contributes to: Multi-Language Hook Support: Python, JavaScript, TypeScript, .NET #7435