fix: address PR #45 review feedback

- Bump version to 0.6.0 (rebase on main which is at 0.5.0)
- Remove @ prefix from backstage-upgrade in routing table
- Add dependency note for cross-skill version reference
- Add cross-references between NFS guide and skill references

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

Author: rohitkrai03

docs/nfs-migration-guide.md

@@ -2,6 +2,8 @@
 
 A practical guide for Red Hat Developer Hub plugin authors migrating from the legacy Backstage frontend system to NFS.
 
+> **Agent skill users:** The `nfs-migration` skill (`skills/nfs-migration/`) contains the same patterns broken into reference files optimized for agent consumption. This guide is the authoritative human-readable source. When updating migration patterns, update this guide first, then sync the corresponding reference file.
+
 ---
 
 ## 1. What is the New Frontend System

skills/backstage-upgrade/references/determine-target.md

@@ -4,6 +4,8 @@
 
 RHDH pins a specific Backstage version per release. Load the version matrix from `../../rhdh/references/versions.md` to find the mapping.
 
+> **Dependency:** RHDH version alignment requires the `rhdh` core skill to be installed alongside this skill. If `versions.md` is not found at that path, ask the user for the target RHDH and Backstage versions directly.
+
 Ask the user: **"Which RHDH version are you targeting?"**
 
 | RHDH Version | Backstage Version |

skills/nfs-migration/SKILL.md

@@ -10,6 +10,8 @@ description: >
   to the new frontend system for RHDH.
 ---
 
+> **Human-readable guide:** `docs/nfs-migration-guide.md` is the authoritative source for migration patterns. These reference files are optimized for agent consumption. When patterns diverge, the guide takes precedence.
+
 <essential_principles>
 
 <principle name="discover_first">