VST3 third-party plugins fail to load via load_instrument_or_effect URI

[yaxloco]

Bug Report

Environment

• Ableton Live 12
• Windows 11
• AbletonMCP (latest)

Description

Third-party VST3 plugins are listed correctly in the browser via
get_browser_items_at_path with is_loadable: true, but calling
load_instrument_or_effect with their exact URI returns:

"Browser item with URI '...' not found"

Plugins tested (all fail)

• Serum 2 → query:Plugins#VST3:Xfer%20Records:Serum%202
• FabFilter Pro-Q 4 → query:Plugins#VST3:FabFilter:Pro-Q%204
• ValhallaRoom → query:Plugins#VST3:Valhalla%20DSP:ValhallaRoom

What works

• Native Ableton instruments load fine (Operator, Wavetable, etc.)
• URI format tested both with %20 encoding and raw spaces — both fail

Expected behavior

VST3 plugins marked as is_loadable: true in the browser should
load successfully via their URI.

Possible cause

The Remote Script may not be resolving encoded URIs for the
query:Plugins#VST3 category correctly.

[FocusMode-coder]

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