fix(desktop): persist sidebar folder collapse state across view switches (#5631) - #5632

Expanded folders reset whenever the side bar switched to the table of
contents or search, because a component-local collapse ref is thrown away
with the `v-if`ed tree. The state lives on the tree node now, so this locks
the behaviour down: expand two nested folders, switch views, come back, and
both are still expanded.

Ported from the regression spec contributed in #5632, which is the same fix
this branch needed as a prerequisite for #528. It drives the app the same way
as the reveal spec instead of passing the fixture as a launch argument — the
launcher always passes the app path first, so a second directory would open a
second window — and both specs now share an `openProjectFolder` helper.

Co-authored-by: A. S. <[email protected]>

Open a document in a deep folder, collapse that folder, switch to another file
and back: there was no way to find it again. The title bar shows the path but is
not navigable, while Atom, IntelliJ and VS Code all reveal the active file in
their project tree.

Reveal it the way VS Code's Explorer does for `explorer.autoReveal`:

- expand only the folders leading to the file, never collapsing anything;
- scroll only when the row is not already fully visible, then centre it, using
  the same formula as `ListWidget.reveal(index, 0.5)`;
- leave the caret, the tree selection and `activeItem` alone, so F2 and Delete
  keep acting on what the user picked;
- do nothing while the file list is off screen, and reveal again as soon as it
  is visible.

A single watcher on `currentFile` drives it, so every existing way of switching
files — tab click, cycle, quick open, sidebar click, startup restore — gets the
behaviour without touching those call sites. Moving the folder collapse state
onto the tree node (#5632) is what lets the store expand ancestors before the
render instead of racing freshly mounted folder components.

Also adds `autoRevealInSidebar` (on by default), a "Show in Side Bar" tab
context-menu entry and a `file.reveal-in-sidebar` command for the manual case,
with unit tests for the expansion and scroll maths and an e2e spec that drives
the real app against a generated project.

Open a document in a deep folder, collapse that folder, switch to another file
and back: there was no way to find it again. The title bar shows the path but is
not navigable, while Atom, IntelliJ and VS Code all reveal the active file in
their project tree.

Reveal it the way VS Code's Explorer does for `explorer.autoReveal`:

- expand only the folders leading to the file, never collapsing anything;
- scroll only when the row is not already fully visible, then centre it, using
  the same formula as `ListWidget.reveal(index, 0.5)`;
- leave the caret, the tree selection and `activeItem` alone, so F2 and Delete
  keep acting on what the user picked;
- do nothing while the file list is off screen, and reveal again as soon as it
  is visible.

A single watcher on `currentFile` drives it, so every existing way of switching
files — tab click, cycle, quick open, sidebar click, startup restore — gets the
behaviour without touching those call sites. Moving the folder collapse state
onto the tree node (#5632) is what lets the store expand ancestors before the
render instead of racing freshly mounted folder components.

Also adds `autoRevealInSidebar` (on by default), a "Show in Side Bar" tab
context-menu entry and a `file.reveal-in-sidebar` command for the manual case,
with unit tests for the expansion and scroll maths and an e2e spec that drives
the real app against a generated project.

Open a document in a deep folder, collapse that folder, switch to another file
and back: there was no way to find it again. The title bar shows the path but is
not navigable, while Atom, IntelliJ and VS Code all reveal the active file in
their project tree.

Reveal it the way VS Code's Explorer does for `explorer.autoReveal`:

- expand only the folders leading to the file, never collapsing anything, and
  only once the file is known to be in the tree;
- scroll only when the row is not already fully visible, then centre it, using
  the same formula as `ListWidget.reveal(index, 0.5)`;
- leave the caret, the tree selection and `activeItem` alone, so F2 and Delete
  keep acting on what the user picked;
- do nothing while the file list is off screen, and retry as the tree fills in,
  so a project opened or restored after that file is revealed as well.

A single watcher on `currentFile` plus the tree's change counter drives it, so
every existing way of switching files — tab click, cycle, quick open, sidebar
click, startup restore — gets the behaviour without touching those call sites.
Moving the folder collapse state onto the tree node (#5632) is what lets the
store expand ancestors before the render instead of racing freshly mounted
folder components.

Also adds `autoRevealInSidebar` (on by default), a "Show in Side Bar" tab
context-menu entry and a `file.reveal-in-sidebar` command for the manual case,
with unit tests for the expansion and scroll maths and an e2e spec that drives
the real app against a generated project.

…#5654)

Open a document in a deep folder, collapse that folder, switch to another file
and back: there was no way to find it again. The title bar shows the path but is
not navigable, while Atom, IntelliJ and VS Code all reveal the active file in
their project tree.

Reveal it the way VS Code's Explorer does for `explorer.autoReveal`:

- expand only the folders leading to the file, never collapsing anything, and
  only once the file is known to be in the tree;
- scroll only when the row is not already fully visible, then centre it, using
  the same formula as `ListWidget.reveal(index, 0.5)`;
- leave the caret, the tree selection and `activeItem` alone, so F2 and Delete
  keep acting on what the user picked;
- do nothing while the file list is off screen, and retry as the tree fills in,
  so a project opened or restored after that file is revealed as well.

A single watcher on `currentFile` plus the tree's change counter drives it, so
every existing way of switching files — tab click, cycle, quick open, sidebar
click, startup restore — gets the behaviour without touching those call sites.
Moving the folder collapse state onto the tree node (#5632) is what lets the
store expand ancestors before the render instead of racing freshly mounted
folder components.

Also adds `autoRevealInSidebar` (on by default), a "Show in Side Bar" tab
context-menu entry and a `file.reveal-in-sidebar` command for the manual case,
with unit tests for the expansion and scroll maths and an e2e spec that drives
the real app against a generated project.