fix(search-form): enable search input for keyboard accessibility

[arthurgousset]

Summary

Fixes WCAG 2.1.1 (Keyboard) and WCAG 2.4.3 (Focus Order) violations by making the search input field keyboard accessible while preventing focus trap issues.

Issues Resolved: #23, #77 (duplicates describing the same problem)

Problem: The search input field had a disabled attribute that blocked keyboard users from accessing core search functionality on the Zanichelli homepage.

Solution: Removed the disabled attribute and implemented proper focus management using aria-hidden and tabIndex to prevent focus when the field is visually hidden.

Changes

Search Input Field (search-form.tsx)

• Removed: disabled={!this.showSearchbar} attribute from input element
• Added: aria-label="Cerca per parola chiave o ISBN" for screen reader support
• Added: aria-hidden={!this.showSearchbar ? 'true' : undefined} to hide from AT when closed
• Added: tabIndex={!this.showSearchbar ? -1 : 0} to remove from tab order when closed

Reset Button (consistency improvement)

• Removed: disabled={!this.showSearchbar} attribute
• Added: aria-hidden and tabIndex pattern matching input field

Test Plan

• Verified search field receives keyboard focus on page load
• Confirmed keyboard input works (typed "matematica" successfully)
• Tested Tab key navigation - field is in tab order when visible
• Verified field is NOT in tab order when visually hidden (no focus trap)
• Confirmed accessibility tree shows no [disabled] attribute
• Tested with screen reader context (aria-label provides proper context)
• Code review passed with no critical issues

Evidence

View before/after screenshots, accessibility trees, and full verification results:
https://app.workback.ai/dashboard/issue/23/

Key Results:

• ✅ Before: searchbox "Cerca per parola chiave o ISBN" [disabled]
• ✅ After: searchbox "Cerca per parola chiave o ISBN" (enabled, properly managed)
• ✅ Focus test: {"disabled": false, "focused": true, "canReceiveFocus": true}
• ✅ Keyboard input test: Successfully typed "matematica"
• ✅ No focus trap when hidden

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WCAG References:

• 2.1.1 Keyboard (Level A)
• 2.4.3 Focus Order (Level A)