docs: update CHANGELOG.md for 0.2.0-alpha release

CHANGELOG.md

@@ -8,6 +8,15 @@ The format is based on [Keep a Changelog](https://keepachangelog.com/en/1.1.0/),
 
 - No unreleased changes yet; add items here as you work toward the next release.
 
+## [0.2.0-alpha] - 2026-02-11
+
+### Added
+
+- **Visitor ID storage: optional localStorage for cross-tab unique visitors (PULSE-51).**
+  - Default: cross-tab visitor ID in `localStorage` so the same person with multiple tabs/windows (same origin) is counted as one visitor. Optional `data-storage-ttl` attribute sets TTL in hours; after expiry the script regenerates the ID.
+  - Optional `data-storage="session"` opts out to per-tab (ephemeral) counting using `sessionStorage`, preserving the previous privacy-first, no-persistent-ID behaviour when desired.
+  - Script embed snippet and dashboard copy updated to describe the default and the opt-out. No backend or schema changes; events remain keyed by `session_id`.
+
 ## [0.1.0] - 2026-02-09
 
 ### Added
@@ -17,5 +26,6 @@ The format is based on [Keep a Changelog](https://keepachangelog.com/en/1.1.0/),
 
 ---
 
-[Unreleased]: https://github.com/ciphera-net/pulse/compare/v0.1.0...HEAD
+[Unreleased]: https://github.com/ciphera-net/pulse/compare/v0.2.0-alpha...HEAD
+[0.2.0-alpha]: https://github.com/ciphera-net/pulse/compare/v0.1.0...v0.2.0-alpha
 [0.1.0]: https://github.com/ciphera-net/pulse/releases/tag/v0.1.0