fix: Make Branch Output batch hotkeys work when the status dock is hidden

[hanatyan128]

Summary

Fixes #148. The global "Add chapter to all branch outputs" hotkey (and the other
*All batch hotkeys) silently did nothing for Branch Output while the same key kept
working for vanilla OBS recording.

Root cause

BranchOutputStatusDock::addChapterToRecordingAll() and its siblings gated each
filter on row->status->isAddChapterToRecordingButtonShow(). That value is the
dock button's visibility, refreshed only by the dock's 2-second timer, which runs
only while the dock widget is visible (showEvent/hideEvent, and the
constructor's if (isVisible())). The button's initial state is invisible. So when
the status dock is hidden/closed, the visibility flag is never updated and every
batch hotkey skips all filters — even though recording is active and the per-filter
action would succeed. The vanilla OBS chapter marker is an independent path and is
unaffected, matching the attached logs in the issue (only adv_file_output receives
chapters before the workaround; all outputs receive them after).

Changes

• Remove the per-row button-visibility gate from splitRecordingAll,
  pauseRecordingAll, unpauseRecordingAll, addChapterToRecordingAll,
  saveReplayBufferAll. Each filter action already self-guards under outputMutex
  and re-checks real output state, so unconditional per-row dispatch (filtered only
  by row output type) is correct and dock-visibility independent.
• Initialize addChapterToRecordingEnabled in the BranchOutputFilter constructor.
  It was the only recording-context flag left uninitialized, allowing an
  indeterminate read before the first recording start.

Verification

• Incremental build (RelWithDebInfo, Windows x64) succeeds.
• clang-format applied.
• Parallel code review run; no Critical/Major findings. Minor (-Wreorder) and the
  comment-discipline Info finding were addressed in this branch.

Manual testing recommended: with the Branch Output status dock hidden, start
recording (Interlock Recording) and confirm the global chapter / split / pause /
replay-buffer hotkeys act on all active Branch Output filters.

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