[jhodapp]

Description

Second of five PRs for the stepped "New session" dialog. Adds the dialog's leaf controls, presentational and tested, not mounted anywhere yet. Stacked on #522.

Changes

• Controls (ui/new-session/): MonthGrid (Monday-first, past days disabled, Today pill, busy dots, 350ms day tooltip, arrow-key focus), DurationField (30/45/50/60 chips + stepper, 15–180 in steps of 5), TimeField (suggested time chips + time input), BusyNote ("Already on …" list or the overlap pill with "Use 3:30 PM instead"), PersonPicker (search over everyone, active people first, Show everyone / Hide inactive), WeekdayPicker (start day locked).
• Primitives: Chip size="md", Button sizes icon-md (44) and icon-lg (48), Toggle variant="round", RadioCardItem, CheckDisc.
• Hooks/utils: useMediaQuery, useHoverIntent, a shared prefersReducedMotion() (replaces the private copies in the toast pill and global search).
• Hit targets: a modal Tailwind screen at 900px; every control is ≥44px below it and drops to the design's 36/40px above it. Style guide notes the 36px chip.

Screenshots / Videos Showing UI Changes (if applicable)

None yet; nothing renders these until the dialog PR.

Testing Strategy

• 51 new component and hook tests written as the spec before the code; all 2608 tests pass, tsc and lint clean.
• Toast pill and global search tests pass unedited after the reduced-motion swap.

Concerns

• src/components/hooks/use-mobile.tsx has no tracked users but stays for now; a local gitignored prototype still imports it.