[griffithtp]

Summary

• Split each Terminal window's isolated dashboard list into a shared,
  process-wide DashboardRegistry + per-window DashboardSession, so
  multiple Terminal windows in the same process see the same dashboards
  live (create/rename/close/reopen/delete/reorder broadcast instantly).
• Added a single shared dashboards.json persistence file with a
  one-time migration that merges every pre-existing per-terminal
  dashboard list, disambiguating name collisions.
• Added an in-memory active-dashboard exclusivity lock so the same
  dashboard can never be edited live in two windows at once, with
  "Duplicate" and "Move here" actions when a dashboard is locked
  elsewhere.
• Frontend: lock indicators on the dashboard switcher/Manage drawer and
  a non-blocking conflict banner with the two resolution actions.
• Kept each Terminal window launched from Desktop Agent as an
  independent OS process (per-process sharing only applies within one
  process) — added lightweight cross-process instance discovery so a
  dashboard can be explicitly duplicated from one running instance into
  another without merging their state or process lifecycles.
• Scaffolder: versions.json migration (0.1.12) covering the changed
  backend files, verified against a simulated upgrade of an old
  workspace.

Test plan

• cargo check --workspace / cargo test --workspace (31 tests)
• npx tsc --noEmit
• npm run check-template-drift
• Scaffolded a workspace on the prior version, ran the upgrade CLI,
  confirmed the migrated files match source and cargo check --workspace passes in the upgraded workspace
• Manual: two Terminal instances from the launcher — confirm each
  stays independent, and "Duplicate from another Terminal" pulls a
  dashboard from one into the other without changing the source