Problem

WidgetAvailability.ts already defines minVersion for each widget, but this data is not used anywhere. When a user on an older GitLab instance (e.g., 15.x) tries to use a widget that requires 17.0+, they get a raw API error instead of a clear message.

Current State

• WidgetAvailability.ts has version requirements per widget (e.g., CUSTOM_FIELDS: { minVersion: 17.0 })
• GitLabVersionDetector.ts already detects instance version
• Neither is connected to the work items handler

Target State

Use WidgetAvailability.isWidgetAvailable() at runtime in manage_work_item handler to validate that the requested widget parameters are supported by the target GitLab instance version.

Validation Flow

User requests manage_work_item with weight parameter
  → Map parameter to widget type (weight → WEIGHT)
  → Check WidgetAvailability.isWidgetAvailable("WEIGHT")
    → Check minVersion against detected instance version
    → Check tier (handled by #136 at schema level, but double-check here)
  → If unavailable: return structured error with required version + upgrade hint
  → If available: proceed with API call

Error Response

{
  "error": "Widget 'CUSTOM_FIELDS' requires GitLab >= 17.0 (detected: 16.5.0)",
  "widget": "CUSTOM_FIELDS",
  "required_version": "17.0",
  "detected_version": "16.5.0",
  "docs_url": "https://docs.gitlab.com/..."
}

Implementation

• Add parameter-to-widget mapping in handler or schema definition
• Call WidgetAvailability.isWidgetAvailable(widgetType) before constructing GraphQL input
• Return VERSION_RESTRICTED structured error (extend error-handler.ts)
• Keep WidgetAvailability.ts as the source of truth for version requirements

Relationship to Other Issues

• feat(workitems): extend manage_work_item with date, time tracking, and tier-specific widgets #135 — adds the widget parameters
• feat(availability): extend tier matrix with per-parameter gating #136 — gates parameters by TIER at schema level (build time)
• This issue — gates parameters by VERSION at runtime (before API call)

Together: schema shows only tier-appropriate params, runtime validates version compatibility.