feat: search autocomplete — dropdown suggestions as user types item name

## Problem

The current panel search requires typing the exact item name and pressing Enter. There is no autocomplete or suggestion dropdown.

## Blocker

The WFM public API does not expose a `/v1/items` list endpoint (returns 404). A static items list must be bundled with the extension.

## Proposed approach

1. Scrape or obtain the full WFM item list (slug + display name)
2. Bundle as a compressed JSON file in the extension
3. Load on panel start, filter as user types, show dropdown
4. Update the bundled list on each release

## Acceptance criteria

- [ ] Dropdown appears as user types (min 2 chars, debounced 200ms)
- [ ] Results sorted: starts-with match first, then contains
- [ ] Max 12 results shown
- [ ] Arrow keys + Enter to select
- [ ] Escape closes dropdown
- [ ] Bundled items list is up to date at release time

No files or tests are named. Start by locating the panel's current exact-name search and the extension's asset-loading and release configuration, then verify the WFM API limitation and the source for the bundled slug/display-name list. Done means the debounced, keyboard-accessible dropdown meets all listed matching, result-count, dismissal, and release-freshness criteria.

Written by the indexing model from the issue text.