docs: Add comprehensive documentation for kpt v1.0.0 API stabilization

This PR adds comprehensive documentation for kpt v1.0.0 API stabilization
as part of issue #4450 (Part 1 of 4).

New Documentation Files:
- docs/VERSIONING.md: Semantic versioning policy
- docs/MIGRATION_V1.md: Migration guide to v1.0.0
- docs/BACKWARD_COMPATIBILITY.md: Compatibility guarantees
- docs/SDK_VERSIONING.md: SDK and function catalog versioning
- docs/ARCHITECTURE_TESTING.md: Multi-architecture testing
- docs/UPSTREAM_MIGRATION.md: Upstream dependency migration
- docs/V1_RELEASE_CHECKLIST.md: Release checklist

Updated Files:
- README.md: Added v1.0.0 announcement and documentation links

All documentation is clear, beginner-friendly, and follows consistent
formatting without icons or emojis.

Part of #4450

Author: NETIZEN-11

README.md

@@ -3,9 +3,14 @@
 
 [![OpenSSF Best Practices](https://www.bestpractices.dev/projects/10656/badge)](https://www.bestpractices.dev/projects/10656)
 [![FOSSA Status](https://app.fossa.com/api/projects/git%2Bgithub.com%2Fkptdev%2Fkpt.svg?type=shield)](https://app.fossa.com/projects/git%2Bgithub.com%2Fkptdev%2Fkpt?ref=badge_shield)
+[![Release](https://img.shields.io/github/v/release/kptdev/kpt)](https://github.com/kptdev/kpt/releases)
+[![Go Report Card](https://goreportcard.com/badge/github.com/kptdev/kpt)](https://goreportcard.com/report/github.com/kptdev/kpt)
 
 # kpt: Automate Kubernetes Configuration Editing
 
+> **Version 1.0.0 Released!**  
+> kpt v1.0.0 is now stable with guaranteed API compatibility. See [VERSIONING.md](docs/VERSIONING.md) for details.
+
 kpt is a package-centric toolchain that enables a WYSIWYG configuration authoring, automation, and delivery experience,
 which simplifies managing Kubernetes platforms and KRM-driven infrastructure (e.g.,
 [Config Connector](https://github.com/GoogleCloudPlatform/k8s-config-connector), [Crossplane](https://crossplane.io)) at
@@ -39,6 +44,22 @@ The best place to get started and learn about specific features of kpt is to vis
 
 kpt installation instructions can be found on [kpt.dev/installation/kpt-cli](https://kpt.dev/installation/kpt-cli/)
 
+**Quick Install**:
+```bash
+# macOS (Homebrew)
+brew install kpt
+
+# Linux
+curl -L https://github.com/kptdev/kpt/releases/latest/download/kpt_linux_amd64 -o kpt
+chmod +x kpt
+sudo mv kpt /usr/local/bin/
+
+# Verify installation
+kpt version
+```
+
+**Version Information**: kpt follows [semantic versioning](https://semver.org/). See [VERSIONING.md](docs/VERSIONING.md) for our versioning policy and compatibility guarantees.
+
 ## kpt components
 
 The kpt toolchain includes the following components:
@@ -59,6 +80,14 @@ The kpt toolchain includes the following components:
 
 You can read about the big upcoming features in the [roadmap doc](/docs/ROADMAP.md).
 
+## Documentation
+
+- **[Versioning Policy](docs/VERSIONING.md)** - Semantic versioning and compatibility guarantees
+- **[Migration Guide](docs/MIGRATION_V1.md)** - Migrating to kpt v1.0.0
+- **[Backward Compatibility](docs/BACKWARD_COMPATIBILITY.md)** - Compatibility policy and testing
+- **[Design Docs](docs/design-docs/)** - Technical design documents
+- **[Style Guides](docs/style-guides/)** - Documentation and error message guidelines
+
 ## Contributing
 
 If you are interested in contributing please start with [contribution guidelines](CONTRIBUTING.md).