docs: add policy-as-code tutorial chapters 6-7 (testing & versioning) (#916)

* docs: add MIT license headers to chapters 1-4 files

Normalize license headers across all tutorial chapters.
Chapters 5-7 already had them; this adds them to chapters
1-4 markdown and YAML example files for consistency.

* docs: add policy-as-code tutorial chapter 6 (policy testing)

Covers structural validation with Pydantic, declarative YAML
test scenarios, cross-policy test matrices, and regression
detection. Includes runnable Python example and test fixtures.

* docs: add policy-as-code tutorial chapter 7 (policy versioning)

Covers side-by-side version comparison, structural diffing,
behavioral regression detection, and deploy gates. Updates
README to link chapters 6-7 and fixes chapter 5 nav link.

Author: harinarayansrivatsan

docs/tutorials/policy-as-code/01-your-first-policy.md

@@ -1,3 +1,6 @@
+<!-- Copyright (c) Microsoft Corporation. -->
+<!-- Licensed under the MIT License. -->
+
 # Chapter 1: Your First Policy
 
 In this chapter you will write a YAML policy file that blocks dangerous agent

docs/tutorials/policy-as-code/02-capability-scoping.md

@@ -1,3 +1,6 @@
+<!-- Copyright (c) Microsoft Corporation. -->
+<!-- Licensed under the MIT License. -->
+
 # Chapter 2: Capability Scoping
 
 In Chapter 1 you created a single policy that applies to every agent. In

docs/tutorials/policy-as-code/03-rate-limiting.md

@@ -1,3 +1,6 @@
+<!-- Copyright (c) Microsoft Corporation. -->
+<!-- Licensed under the MIT License. -->
+
 # Chapter 3: Rate Limiting
 
 An agent with the right permissions can still cause problems if it runs out of

docs/tutorials/policy-as-code/04-conditional-policies.md

@@ -1,3 +1,6 @@
+<!-- Copyright (c) Microsoft Corporation. -->
+<!-- Licensed under the MIT License. -->
+
 # Chapter 4: Conditional Policies
 
 In Chapters 1-3 each policy stood on its own — one file, one evaluator, one

docs/tutorials/policy-as-code/05-approval-workflows.md

@@ -463,5 +463,5 @@ every tool gets the right decision in every environment. That is policy
 testing.
 
 **Previous:** [Chapter 4 — Conditional Policies](04-conditional-policies.md)
-**Next:** Chapter 6 — Policy Testing (coming soon) — verify that every
+**Next:** [Chapter 6 — Policy Testing](06-policy-testing.md) — verify that every
 policy rule works correctly, automatically.