Greptile Summary

This PR adds Luau (Roblox's typed Lua dialect) syntax highlighting to the editor by introducing a new StreamLanguage CodeMirror mode (src/cm/modes/luau/index.ts) and wiring it up through supportedModes.ts and a CSS file-type icon. The implementation is comprehensive and fits cleanly into the existing mode-registration pattern.

Two logic bugs were found:

• Double-indentation for for loops: "for" is included in indentTokens alongside "do", but every Luau for loop always ends with do on the same line, so indentDepth is incremented twice per loop, making the body doubly indented and leaving a residual +1 depth after the closing end.
• type(value) argument misclassified: After tokenizing the type keyword, state.expectTypeName is set but is never cleared when an opening ( is encountered, so type(value) — a common built-in call — incorrectly highlights its first argument as a type-definition name.

A commented-out 36-line Luau LSP server configuration block remains in serverRegistry.ts, which should be removed or addressed in a follow-up.

Confidence Score: 2/5

• The feature is net-new and isolated, so bugs cannot cause regressions; however, both tokenizer logic bugs are readily reproducible on ordinary Luau code and should be fixed before merge.
• Safe to merge for basic syntax highlighting, but two logic bugs in the tokenizer will produce visible incorrect indentation and wrong token colouring for common Luau patterns: every for loop body will be double-indented (with residual +1 depth after closing end), and every type(x) call will mis-colour its first argument. These are worth fixing before merge.
• src/cm/modes/luau/index.ts — fix the for/do indentation double-count and the type(...) argument misclassification; src/cm/lsp/serverRegistry.ts — remove or address the commented-out LSP configuration block.

_{Last reviewed commit: b876f54}

@greptileai