feat(office): add Workspace TUI with shared bootstrap and test suite

Introduce the office Bubble Tea browser (module tree, multi-select lists,
markdown preview) alongside oo, with cmd/internal/bootstrap for shared auth,
unit tests across preview/model/ui/fetch, CI build for both binaries, and
GoReleaser archives for office.

Co-authored-by: Cursor <cursoragent@cursor.com>

cmd/office/model/item.go

@@ -0,0 +1,114 @@
+package model
+
+// Kind identifies the OnlyOffice entity type for list items and preview routing.
+type Kind string
+
+const (
+	KindProject     Kind = "project"
+	KindTask        Kind = "task"
+	KindContact     Kind = "contact"
+	KindOpportunity Kind = "opportunity"
+	KindCase        Kind = "case"
+	KindCRMTask     Kind = "crm_task"
+	KindMail        Kind = "mail"
+	KindEvent       Kind = "event"
+	KindCalendar    Kind = "calendar"
+	KindFile        Kind = "file"
+	KindUser        Kind = "user"
+)
+
+// Subject identifies a menu leaf / list source.
+type Subject string
+
+const (
+	SubjectProjects      Subject = "projects"
+	SubjectTasks         Subject = "tasks"
+	SubjectCalendars     Subject = "calendars"
+	SubjectEvents        Subject = "events"
+	SubjectContacts      Subject = "contacts"
+	SubjectPersons       Subject = "persons"
+	SubjectCompanies     Subject = "companies"
+	SubjectOpportunities Subject = "opportunities"
+	SubjectCases         Subject = "cases"
+	SubjectCRMTasks      Subject = "crm_tasks"
+	SubjectMailInbox     Subject = "mail_inbox"
+	SubjectMailSent      Subject = "mail_sent"
+	SubjectMailDrafts    Subject = "mail_drafts"
+	SubjectMailTrash     Subject = "mail_trash"
+	SubjectMailSpam      Subject = "mail_spam"
+	SubjectProjectFiles  Subject = "project_files"
+	SubjectTaskFiles     Subject = "task_files"
+	SubjectUsers         Subject = "users"
+)
+
+// FocusPane is which column has keyboard focus.
+type FocusPane int
+
+const (
+	FocusMenu FocusPane = iota
+	FocusList
+	FocusPreview
+)
+
+// NextFocusPane cycles menu → list → preview → menu.
+func NextFocusPane(p FocusPane) FocusPane {
+	switch p {
+	case FocusMenu:
+		return FocusList
+	case FocusList:
+		return FocusPreview
+	default:
+		return FocusMenu
+	}
+}
+
+// Item is one row in the center list pane.
+type Item struct {
+	ID, Title, Subtitle string
+	Kind                Kind
+	Raw                 map[string]any
+	Selected            bool
+}
+
+// Selection tracks multi-selected item IDs within the current subject.
+type Selection struct {
+	ids map[string]struct{}
+}
+
+// NewSelection returns an empty selection set.
+func NewSelection() *Selection {
+	return &Selection{ids: make(map[string]struct{})}
+}
+
+// Toggle flips selection on items[idx] and updates the ID set.
+func (s *Selection) Toggle(items *[]Item, idx int) {
+	if idx < 0 || idx >= len(*items) {
+		return
+	}
+	it := &(*items)[idx]
+	it.Selected = !it.Selected
+	if it.Selected {
+		s.ids[it.ID] = struct{}{}
+	} else {
+		delete(s.ids, it.ID)
+	}
+}
+
+// Count returns the number of selected items.
+func (s *Selection) Count() int {
+	return len(s.ids)
+}
+
+// Clear removes all selections.
+func (s *Selection) Clear() {
+	s.ids = make(map[string]struct{})
+}
+
+// IDs returns selected item IDs in stable order (map iteration order is fine for display).
+func (s *Selection) IDs() []string {
+	out := make([]string, 0, len(s.ids))
+	for id := range s.ids {
+		out = append(out, id)
+	}
+	return out
+}