Offer only unarchived projects, weightiest first, when creating a task

[MJohnson459]

The project picker that opens when creating a task listed every project in the store, archived ones included, ordered alphabetically. Both halves were wrong. Store::create_task refuses an archived project (DESIGN.md §5), so offering one is offering a choice that can only fail — and in the Editor and Plan flows it fails late, after the operator has written the task out in $EDITOR or sat through a planning session. Alphabetical order also says nothing about which project the operator is working on this week; project weight already carries that answer (§7) and is what they edit every morning.

What changed

voro_core::projects_for_new_task (crates/voro-core/src/model.rs) is a pure helper over an already-loaded &[Project]: it drops archived projects and returns the rest weight-descending, name-ascending within a weight. It lives in core because the ordering is business logic, not rendering, and takes a slice rather than issuing a second query because App refreshes self.projects every tick. Store::projects() is untouched and keeps its name ordering — the projects screen, the header, and voro project list all depend on it.

All three create flows route through it. App::creatable_projects wraps the helper, and new_task now branches on the length of the filtered list: one live project beside archived ones goes straight to start_create on the live one rather than opening a picker, and a store whose every project is archived opens no picker and no longer fires NO_PROJECTS_HINT — it leaves a new ALL_PROJECTS_ARCHIVED_HINT status line pointing at the projects screen and the A key that unarchives, in the same no-op-with-an-explanation style as the neighbouring keys. key_pick_project and the Mode::PickProject draw arm both index the filtered list, so sel means the same thing to each; the mouse path needed no change, since clicks route through Hit::PickerOption into the same sel. Each picker row carries its weight ahead of the name, as the projects screen does ( 4 zeta), so weightiest-first reads as an order rather than a shuffle, and the popup widens from 44 to 48 columns to fit it.

Parked projects stay on the list — weight 0 is a snooze, not a retirement (§5) — and simply sort last. The cockpit/task-browser gate that fires while no project is registered still counts all projects, archived included, and the CLI is untouched: voro add names its project explicitly and create_task already refuses an archived one.

DESIGN.md §9 gains a passage recording that the create keys ask which project only when there is a choice, offer only projects that can take the work, and order them weightiest first — enforcement of §5's existing rule rather than a new one. CHANGELOG has an entry under Unreleased/Changed.

Verification

cargo test --workspace — 849 tests, all passing, including new ones: voro-core unit tests that archived projects are excluded at any weight and that ordering is weight-then-name with a parked project kept and sorted last; voro tests that n with one unarchived project beside three archived ones opens the create modal directly on the live one, that n/N with every project archived open no picker and leave the explanatory status, and that ⏎ on the picker's nth row starts the create flow on the project the filtered order puts there rather than the alphabetical one; and a ui.rs render test that the picker shows weights and omits an archived project's name despite it outweighing every row shown.

cargo clippy --workspace --all-targets -- -D warnings and cargo fmt --all clean.