* feat(plugins): add Todoist import plugin with Import/Export launcher
* fix(plugins): fix cross-chunk subtask loss in todoist-import + hardening
* fix(plugins): clamp non-finite Todoist durations + review polish
* feat(plugins): add Eisenhower priority mapping to Todoist import
Replace the single "map priorities to p1-p3 tags" checkbox with one
mutually-exclusive control (Nothing / p1-p3 tags / Eisenhower matrix).
The new Eisenhower option reuses SP's built-in urgent/important tags by
title (p1 -> urgent+important, p2 -> important, p3 -> urgent, p4 -> none),
so imported tasks populate the Eisenhower Matrix board with no new tag
and no new plugin API. Collapsing Todoist's single priority axis onto the
2-D matrix is opinionated, so it stays opt-in and off by default.
Requested in the review of #8882.
* fix(plugins): harden Todoist import data integrity
* fix(plugins): improve Todoist import feedback
