Improve Planner landing and wide timelines

[callumalpass]

What changed

• simplify the Planner connection screen and remove the marketing-style eyebrow
• make the sample timeline tasks draggable with pointer and keyboard controls
• provide a clearer message when the current Planner origin is not registered
• extend coarse timeline scales to fill wide viewports and update them on resize
• add tests for preview movement and wide timeline bounds

Why

The connection screen copy was more promotional than functional, its sample task bars looked interactive without being movable, and fixed coarse-scale horizons could end before a very wide viewport.

Impact

The landing screen is more direct and its sample timeline is genuinely interactive. Months and Quarters views now fill the available timeline width without changing existing task-derived bounds.

Validation

• pnpm verify
• 34 unit tests
• 2,900px browser verification in Quarters view, with canvas/header/final month boundary reaching the viewport edge