* gui: task board groups tasks by what they need

Derive tasks into four columns (Working, Needs you, In review, Done)
following orchestrator lifecycle states and disposition outcomes. Add
pure card models, dialog view, and semantic styling tokens.

Co-Authored-By: Gemini 3.8 Flash <noreply@google.com>

* gui: wire show-board action, palette shortcut and graphical QA tests

Install win.show-board with <Control><Shift>b shortcut and command
palette integration. Present task board dialog snapshotting model tasks,
focusing pane on card activation, and add Xvfb visual tests.

Co-Authored-By: Gemini 3.8 Flash <noreply@google.com>

* docs: roadmap marks phases 1–2 done and adds task board spec

Mark multiplexer core and agent awareness phases as done on the roadmap,
list specs 001–019 under shipped features, and define the spec 019 task
board specification.

Co-Authored-By: Gemini 3.8 Flash <noreply@google.com>

* gui: board cards activate through the list's row-activated

Co-Authored-By: Claude Opus 5.5 (1M context) <noreply@anthropic.com>

* gui: a board card focuses its pane after the dialog hands focus back

Closing the dialog returned focus to the old pane, and that focus-in
counted as a newer navigation, so the card's focus_pane was dropped.
The board now reports the chosen pane from its closed handler and the
app focuses it on idle. The display test answers pane.get and asserts
the pane actually changes.

Co-Authored-By: Claude Opus 5.5 (1M context) <noreply@anthropic.com>

---------

Co-authored-by: Lucenx9 <185146821+Lucenx9@users.noreply.github.com>
Co-authored-by: Gemini 3.8 Flash <noreply@google.com>
Co-authored-by: Claude Opus 5.5 (1M context) <noreply@anthropic.com>