chore: prepare release 4.3.1

RELEASE_NOTES_TEMPLATE.md

@@ -2,6 +2,19 @@
 
 ## [Unreleased]
 ### Added
+_No unreleased changes yet_
+
+### Changed
+_No unreleased changes yet_
+
+### Fixed
+_No unreleased changes yet_
+
+### Removed
+_No unreleased changes yet_
+
+## [4.3.1] - 2026-03-25
+### Added
 - **Smart Land Bases**: Land count and basic-to-dual ratio are now adjusted automatically based on the commander's speed and color-pip intensity. Controlled by `ENABLE_SMART_LANDS=1` (default on in Docker).
   - **Speed detection**: Commander CMC determines a speed category applied as an offset to the user's configured ideal land count. Fast (CMC < 3) = −2 lands, mid = ±0, slow (CMC > 4) = +2 to +4 scaling with color count.
   - **Profile selection**: Basics-heavy (~60% basics) for 1–2 color / low-pip decks; Balanced for moderate pip density; Fixing-heavy (minimal basics, more duals/fetches) for 3+ color or high-pip pools (≥15 double-pip or ≥3 triple-or-more-pip cards).
@@ -12,10 +25,10 @@
   - Override with `LAND_PROFILE=basics|mid|fixing` or `LAND_COUNT=<n>`. A **Smart Lands** notice in the Land Summary explains the chosen profile.
 
 ### Changed
-_No unreleased changes yet_
+_No changes_
 
 ### Fixed
-_No unreleased changes yet_
+_No changes_
 
 ### Removed
-_No unreleased changes yet_
+_No changes_