[Bug] Plugin install doesn't sync with installed_plugins.json when entry missing

Bug Description

Then describe the bug:

/plugin install says "already installed" but doesn't sync with installed_plugins.json. When settings.json has
an enabled plugin entry but installed_plugins.json is missing it, the install command incorrectly reports
success without adding the missing entry. This causes plugins to appear installed but not load. Fix required
manually editing both ~/.claude/settings.json AND ~/.claude/plugins/installed_plugins.json.

Environment Info

• Platform: darwin
• Terminal: WarpTerminal
• Version: 2.0.56
• Feedback ID: d7fad490-3c41-4720-9d97-3a848a8cd5d8

Errors

[{"error":"Error: NON-FATAL: Lock acquisition failed for /Users/chadwalters/.local/share/claude/versions/2.0.56 (expected in multi-process scenarios)\n    at kN0 (/$bunfs/root/claude:2678:1622)\n    at QCA (/$bunfs/root/claude:2678:1300)\n    at processTicksAndRejections (native:7:39)","timestamp":"2025-12-02T21:49:24.497Z"},{"error":"Error: NON-FATAL: Lock acquisition failed for /Users/chadwalters/.local/share/claude/versions/2.0.56 (expected in multi-process scenarios)\n    at kN0 (/$bunfs/root/claude:2678:1622)\n    at ICA (/$bunfs/root/claude:2676:35354)\n    at async FD7 (/$bunfs/root/claude:2676:37462)\n    at async vx (/$bunfs/root/claude:2678:236)\n    at async <anonymous> (/$bunfs/root/claude:2678:12981)\n    at processTicksAndRejections (native:7:39)","timestamp":"2025-12-02T21:49:36.576Z"}]