2.3.11 Design — Due date field in the create modal (mirror Jira; finding #56)

Depends on: 2.4.11

Resolves finding #56 (Yue: "yes, mirror Jira"). Jira's create-issue dialog collects a Due date; Motir's create modal (2.3.3) does not, and its design (create.pen) omits a Due-date field — so adding one is UI the create-modal design doesn't specify. The planning-time design gate therefore requires this design pass BEFORE the code (2.3.12); 2.3.12 is blocked on it.

Extend the create-modal design under design/work-items/ — a create.mock.html (HTML mockup from the live design system, preferred) OR an updated create.pen + a design-notes.md entry — adding a Due date field row that composes the shipped DatePicker primitive (2.4.11 design / 2.4.12 code) with the create modal's existing label+control row grammar. Placement: after Priority, matching the shipped edit form's field order (Priority → Due date) and Jira. Due date is nullable (placeholder "Select a date", no value by default). Colour only through --el-*; AA-safe.

Scope guard: Due date only. create.pen also designs an Assignee field that was never built (finding #51) — that reconciliation is NOT in scope here; do not add Assignee.

Done: PR #106 merged 2026-06-05, merge commit 8de9cba — design APPROVED (Yue merged ⇒ build 2.3.12 to THIS mockup). design/work-items/create.mock.html (HTML mockup from the live --el-* tokens) + design-notes.md section + surface-table row shipped: the create modal with a NEW Due date row placed AFTER Priority, composing the already-shipped DatePicker (2.4.11/2.4.12) — no new component, only placement + label, mirroring Jira's create dialog + the shipped edit form's Priority→Due date order. Two panels: Due date empty (placeholder) · filled with the calendar open. Nullable default; collect-in-form-state→write-on-create documented for 2.3.12. Render-checklist applied (icon viewBox, field-as-container/Clear-as-sibling, prettier, both panels, light+dark). Assignee (in create.pen, never built — finding #51) explicitly left out of scope. Gates 2.3.12 (now ready).

Acceptance criteria

• A create-modal design asset (create.mock.html or updated create.pen)

• a design-notes.md entry show the Due date field — the DatePicker trigger, its "Due date" label, placement after Priority, and the empty/nullable default.

• Mirrors Jira's create-dialog Due date + the shipped edit-form field order; colour via --el-*; AA-safe.
• Assignee is explicitly left out (finding #51, separate).

Context refs

• design/work-items/create.pen — the create-modal surface to extend (Priority + Assignee designed; no Due date)
• design/work-items/datepicker.mock.html + design-notes.md (2.4.11) — the DatePicker primitive to compose
• The shipped edit form's Priority → Due date → Estimate row order (2.3.6, EditIssueForm) — the field grammar to mirror