BACK-555 - Fix TUI task composer editing bugs and add Ctrl+W word delete

[janosmiko]

Summary

Fixes editing bugs in the TUI task composer (shipped in #791) and brings it to BACK-430 first-slice parity. All four bugs trace to neo-neo-bblessed defects the composer did not work around, verified against the installed library.

Bugs fixed

Bug	Root cause	Fix
Backspace was a no-op in Description	textarea.ts:449 backspace branch is empty under fullUnicode, which createScreen always sets	Composer owns deletion + render
Backspace looked frozen in Title	textbox.ts:117-122 deletes then returns before the trailing screen.render()	ignoreKeys on the textbox + composer owns deletion + render
Status picker preselected "Draft"	list.ts:47 hardcodes selected = 0 and ignores the selected option, so the picker always opened on index 0 (Draft)	picker.select(selectedIndex) in shared filter-popup.ts
j/k didn't navigate pickers	list.ts:119/124 bind j/k only under vi, which filter-popup never set	vi: true in shared filter-popup.ts

The filter-popup.ts fixes also correct the board's own filter popups, which had the same preselection and j/k gaps.

Added

• Ctrl+W deletes the previous word in Title and Description.

Parity

• Resting Status now resolves via getDefaultCreateStatus (exported from task-wizard.ts), matching the CLI wizard's canonical "To Do" instead of a literal statuses[0].

Tests

• Pure helpers deleteLastChar / deleteLastWord.
• Resting-status resolves to canonical "To Do" when present but not first.
• Rendered-harness behavioral tests: Backspace and Ctrl+W edit both Title and Description; the status picker preselects the current value so Enter keeps it (returns "To Do", not "Draft").

Verification

• bunx tsc --noEmit clean
• bun run check . clean
• bun test: 1781 pass / 4 skip / 2 fail — the two failures (freezes selected task bytes, runs post-commit hooks against the real index) are pre-existing git-hook tests that also fail on a clean main checkout, unrelated to this change.

Note: j/k navigation is a TUI-only interaction the test harness can't drive (list nav binds on the raw keypress event); verified manually.