docs(CHANGES) Note tmux version deprecation warning

Author: tony

CHANGES

@@ -32,7 +32,16 @@ $ uvx --from 'libtmux' --prerelease allow python
 
 <!-- To maintainers and contributors: Please add notes for the forthcoming version below -->
 
-- _Future release notes will be placed here_
+### Deprecations
+
+- tmux versions below 3.2a are now deprecated and will emit a `DeprecationWarning`
+  on first use. Support for these versions will be removed in a future release.
+  Set `LIBTMUX_SUPPRESS_VERSION_WARNING=1` to suppress the warning.
+
+### Internal
+
+- `TMUX_MAX_VERSION` updated from 3.4 to 3.5a
+- Added `TMUX_SOFT_MIN_VERSION` constant (3.2a) for deprecation threshold
 
 ## libtmux 0.47.0 (2025-11-01)