feat(forge): add Solar LSP command

[decofe]

Motivation

Expose Solar’s language server through forge lsp, so editors can use the same Solar version bundled with Foundry. This supersedes the earlier attempts in #11619, #11277, and #11187 now that solar-lsp is released on crates.io.

Closes #11448.

Changes

• Add the forge lsp subcommand.
• Run Solar 0.2.0’s language server over stdin/stdout.
• Pin solar-lsp alongside Foundry’s existing Solar dependencies.

Testing

• cargo +nightly fmt --all -- --check
• cargo metadata --locked --no-deps --format-version 1
• git diff --check

A full cargo check -p forge was attempted, but the sandbox could not authenticate to the workspace’s patched foundry-rs/optimism Git dependency.

AI assistance

This PR was implemented and drafted with Codex.

Prompted by: @DaniPopes