Add Scala LSP plugin with inline lspServers configuration

[muhsinali]

Summary

Add the Scala LSP plugin using the de facto language server for Scala, Metals, to the official marketplace following the existing conventions set out in a previous PR for pre-existing LSP plugins. This enables the LSP plugin recommendation feature in Claude Code to detect the Scala LSP plugin alongside existing LSP plugins directly from the marketplace.

LSP plugin added

Plugin	Language	Extensions	Binary
scala-lsp	Scala	.sbt, .sc, .scala	metals

Implementation

Following the existing conventions set out in a previous PR for pre-existing LSP plugins:

• The plugin uses strict: false since it only provides LSP configuration
• LSP config is inline in the marketplace entry, not in separate .lsp.json files
• Plugin will be recommended when users edit files with matching extensions AND have the Metals language server binary installed

Test plan

• claude plugin validate . passes
• Test with --plugin-dir pointing to this marketplace
• Verify LSP activates for Scala files when metals binary is installed (see screenshot below)

Example usage

Installation

As mentioned in the README, users need to install the metals binary separately

brew install metals

[muhsinali]

@dhollman @noahzweben @amorriscode @kushal-thakkar would it possible to get a review please?