feat(filter): sort tasks the way the Todoist apps do

[craigcarlyle]

Summary

• td filter view now orders tasks the way the Todoist apps order them, instead of printing whatever order the API returned
• Applies the sorting saved on that filter's view, and falls back to Todoist's default hierarchy when the view has none, which is what "Manual (default)" means in the app
• Adds --sort default|priority|date|deadline|date-added|name|project|assignee|workspace|none and --sort-order asc|desc, with precedence running flag, saved view, Todoist default
• --sort none gives back the raw API order
• Sorts each section of a comma-separated filter on its own, and returns --json / --ndjson in the same order as the pretty output
• Prints the resolved sort in the view header, under Query: and URL:
• Stacked on feat(sort): add task ordering that matches the Todoist apps #480, which adds the two modules this wires up

Why the order was wrong

• Todoist doesn't sort server-side. GET /tasks/filter returns storage order, roughly date added ascending, which is why the reporter found that setting their filter to "date added asc" made the app match the CLI
• Every Todoist client sorts locally, by sorted_by on the view and then by a documented default
• The CLI read neither piece

Not addressed

• grouped_by is still ignored, so a filter grouped by date or label renders flat. That overlaps with feat: expose view options (board/list, group by, sort) — SDK supports view_options_set but the CLI never calls it #462

Test plan

• 11 new tests in the filter suite: saved sort applied, flag overrides it, per-section ordering, JSON path sorted, unreadable view options fall back
• Full suite passes (1838 tests)
• Type-check, lint, format and SKILL.md sync clean
• Manual: a filter whose view is saved with sorted_by: PRIORITY renders p1 first
• Manual: --sort none reproduces the pre-fix order
• Manual: default-sorted filter with date queries leads with date, priority breaks the tie, and a p1 due later still sorts last

$ td filter show <filter-id> --all --json | jq -r '.sections[0].results[] | "p\(5 - .priority)  \(.due.date)"'
p3  2026-08-17
p3  2026-08-17
p4  2026-08-17
p4  2026-08-18
p4  2026-08-19
p4  2026-08-21
p1  2026-08-23

• Manual: --sort assignee across a workspace filter with 13 assignees sorts A-Z with unassigned last, and --sort-order desc reverses to Z-A with unassigned first

Closes #473