fix: complete Personal Pulse heatmap edges

[PANGKAIFENG]

Problem\n\nPersonal Pulse can render a partial first or last week, leaving a visibly missing corner in the 26-week heatmap. The requested mode order is also AI, tasks, consumption, outputs while tasks remains the default.\n\n## Acceptance criteria\n\n- Heatmap always renders exactly 26 columns by 7 rows.\n- Dates outside the available data window use neutral, non-interactive placeholders.\n- Personal Pulse modes render in AI, tasks, consumption, outputs order.\n- Tasks remains selected by default.\n- Regression tests cover the tab order and partial-week edges.\n