feat(pm-wizard): redesign Labels step — Combobox + bulk-create banner

[zbigniewsobiecki]

Summary

The Labels step shipped with three controls per row — dropdown + text input (pre-filled with the same value as the dropdown) + Create button — repeated for every slot whether mapped or not. Visually chaotic, and fresh setup forced 5 sequential Create clicks for the canonical cascade-* labels.

This redesign:

• Searchable Combobox replaces the native <select> for enum-mode rows (Linear + Trello). Each label shows a color swatch so operators can distinguish cascade-* labels at a glance. JIRA (free-text mode) unchanged.
• Bulk-create banner at the top: when ≥1 slot has a default but no mapping, one click creates every missing label with canonical defaults — 5 clicks → 1. Hidden when every slot is mapped or when the provider doesn't declare createLabel. Wires the existing-but-unused createMissingLabelsMutation.
• Per-row Create form collapses once a slot is mapped. Mapped rows show a single clean Combobox. Cuts visual clutter ~50%.

Before / after slot row:

Before (every row, always):
  Ready to Process   [cascade-ready ▾]
                     [cascade-ready            ] [Create label]

After (mapped row):
  Ready to Process   [🔵 cascade-ready ▾]

After (unmapped row):
  Ready to Process   [— Select —                     ▾]
                     [cascade-ready] [Create]    ← secondary

After (top of step, fresh setup):
  ✨ Create 3 missing CASCADE labels with defaults
     cascade-ready · cascade-processed · cascade-auto     [Create all]

Plus ComboboxOption gains an optional swatch?: string field rendered as a 12×12 rounded dot in both the trigger and option rows. Additive; existing callers unchanged.

Test plan

• npm test — 8212 / 8212 (up 2 — net new test count after refactoring the label-mapping suite from 9 SSR tests to 10 element-tree + SSR tests)
• npm run lint — clean
• npm run typecheck — clean
• cd web && npm run build — clean
• Post-merge browser smoke:
  • Linear wizard, fresh setup → bulk banner visible, one click creates all 5, rows collapse to single Combobox each
  • Linear wizard, labels pre-existing → Combobox shows labels with color swatches, mapped rows are compact
  • Trello wizard — same UX improvements apply (shared component)
  • JIRA wizard — free-text Input per slot, no regression

🤖 Generated with Claude Code