Add reusable UX design and observability skills (#10)

docs/implementation.md

@@ -1,5 +1,23 @@
 # Product implementation record
 
+## Reusable UX guidance — task #10
+
+[Task #10](https://git.sendico.io/tech/sxchnge/issues/10), branch `skills-10`,
+adds a concise root UX policy linking two independent skills in `skills/`:
+UX Design covers usable interfaces and its design review; UX Observability covers
+purposeful journey measurement and its observability review. Both preserve product
+conventions and avoid prescribing frameworks, vendors, or visual styles.
+
+Validation: both skills passed `quick_validate.py` from the skill-creator skill;
+root skill links resolve, scaffold checks and `git diff --check` pass. Manual
+review checked the requested principles and checklist coverage, duplication,
+contradictions, and actionable wording. The initial validator attempt lacked
+PyYAML; rerunning in a temporary virtual environment with PyYAML passed.
+
+This is documentation-only guidance, not an implementation or verification of
+product usability or journey instrumentation. Runtime tests and security scans
+were not run. No application behavior or analytics events changed.
+
 ## Scope
 
 The public Astro website now lives in `website/`, preserving its source, assets,