fix: resolve Plot JSON Editor map reset to London on tab focus change (Issue #7)

[IanMayo]

Summary

Fixes Issue #7: "Plot JSON Editor: Map resets to London and loses features when tab loses/regains focus"

This PR resolves the VS Code webview state persistence issue where the Plot JSON Editor map would reset to London coordinates and lose all GeoJSON features when switching between tabs.

Key Changes

• Map State Persistence: Implemented per-file map view state management (center position and zoom level)
• Smart Tab Restoration: Added logic to distinguish between tab activation vs tab restoration from hidden state
• Immediate Feature Loading: Enhanced webview lifecycle to force document updates when tabs are restored
• Optimized Performance: State restoration happens immediately without visual delays or double animations
• Multi-File Support: Each plot file maintains independent state without interference

Technical Implementation

• TypeScript: Enhanced PlotJsonEditorProvider with state management and improved onDidChangeViewState handling
• JavaScript: Added proactive state saving on map interactions and intelligent restoration logic
• Performance: Skip fitBounds when saved state exists to prevent visual flicker

Files Modified

• src/plotJsonEditor.ts - Enhanced webview lifecycle management with state persistence
• media/plotJsonEditor.js - Added state save/restore functionality and optimized restoration timing

Test Plan

• Single plot files restore correctly after tab switches
• Multiple plot files maintain independent states
• Map position and zoom level preserved across tab switches
• GeoJSON features display immediately on tab restoration
• No visual delays or panning animations during restoration
• Feature selections maintained across tab switches
• No interference when switching between visible tabs

Before/After

Before: Tab switches → map resets to London with no features visible
After: Tab switches → map maintains position, zoom level, and displays all features instantly

Closes #7

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• PR: fix: resolve Plot JSON Editor map reset to London on tab focus change (Issue #7) #8

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