v0.61.0 - tmux 3.7a and 3.7b test fixes

libtmux 0.61.0 hardens support for the tmux 3.7 patch line. It fixes Pane.break_pane() naming broken-out windows libtmux instead of tmux's own default on tmux 3.7a/3.7b, and adds get_version_str() for reading the raw tmux version with its point-release suffix intact.

Highlights

• Fix — break_pane() keeps tmux's default window name on 3.7a/3.7b (#699). Breaking a pane into a new window without an explicit window_name left it named libtmux on tmux 3.7a/3.7b; it now keeps tmux's own default (typically the running command). Passing window_name is unaffected.
• New — get_version_str() (#699). libtmux.common.get_version_str() returns the running tmux version verbatim, keeping the point-release suffix ("3.7a") that get_version() strips for numeric comparison — useful for telling patch releases apart, e.g. 3.7 from 3.7a.
• tmux 3.7a/3.7b test compatibility (#698). The test suite now passes against tmux 3.7a and 3.7b, which CI also exercises.

What's Changed

• docs: lead topic pages with the concept, add docs voice guide by @tony in #696
• Fix window-name test for tmux 3.7a/3.7b and add them to CI by @tony in #698
• Fix break_pane forcing 'libtmux' window name on tmux 3.7a/3.7b by @tony in #699

Full Changelog: v0.60.0...v0.61.0