Pr 1724 (#1939)

* feat(coding-agent): add fold/unfold to tree branch navigation

Remap left/right arrow keys in the session tree to jump between branch
segment starts (first child of each branching point). Left on a foldable
node (root or segment start) folds it, hiding its descendants. Right on
a folded node unfolds it. Nested fold state is preserved. Search and
filter changes reset all folds.

Folded branches show ⊞ in the connector (├⊞/└⊞) or as a prefix for
roots. Active path marker • appears after the fold indicator.

Add Page Up/Down support for paging through the tree list, consistent
with session selector and config selector.

* feat(coding-agent): improve tree branch folding closes #1724

---------

Co-authored-by: Sviatoslav Abakumov <dust.harvesting@gmail.com>

packages/coding-agent/CHANGELOG.md

@@ -2,6 +2,9 @@
 
 ## [Unreleased]
 
+### Added
+- Added `/tree` branch folding and segment-jump navigation with `Ctrl+←`/`Ctrl+→` and `Alt+←`/`Alt+→`, while keeping `←`/`→` and `Page Up`/`Page Down` for paging ([#1724](https://github.com/badlogic/pi-mono/pull/1724) by [@Perlence](https://github.com/Perlence))
+
 ### Fixed
 - Fixed custom tool collapsed/expanded rendering in HTML exports. Custom tools that define different collapsed vs expanded displays now render correctly in exported HTML, with expandable sections when both states differ and direct display when only expanded exists ([#1934](https://github.com/badlogic/pi-mono/pull/1934) by [@aliou](https://github.com/aliou))
 - Fixed tmux startup guidance and keyboard setup warnings for modified key handling, including Ghostty `shift+enter=text:\n` remap guidance and tmux `extended-keys-format` detection ([#1872](https://github.com/badlogic/pi-mono/issues/1872))