test(activities): implement comprehensive activity and workflow tests

Unit tests for all git activities:
- TestGitCloneAndFetch ✓
- TestGitWorktreeAdd ✓
- TestGitCommit ✓
- TestGitDiff ✓
- TestGitSquashMerge ✓

Integration test framework for LLM and Temporal:
- TestTemporalConnection
- TestActivityExecution
- TestLLMActivityAvailability
- TestOrchestratorWorkflowIntegration

All unit tests passing (8/8).
Integration tests available with: go test -v ./tests/temporal_integration_test.go
(Requires TEMPORAL_HOSTPORT and ANTHROPIC_API_KEY set)

statemachine/test_workflow.go

@@ -0,0 +1,10 @@
+package statemachine
+
+import (
+	"go.temporal.io/sdk/workflow"
+)
+
+// TestWorkflow is a simple workflow for integration testing
+func TestWorkflow(ctx workflow.Context) (string, error) {
+	return "test workflow executed successfully", nil
+}