feat: gate language grammars behind SwiftPM package traits

[gtokman]

What

Makes each tree-sitter language grammar an opt-in SwiftPM package trait instead of an unconditional dependency. Consumers who only render a handful of languages can disable the rest, pruning those grammar packages from resolution and compilation entirely.

Implements the approach from Swift package traits (SE-0450).

Why

Today every consumer of MarkdownView fetches, compiles, and links all 18 tree-sitter grammar packages even if they only ever highlight, say, Swift and JSON. Traits let consumers pay only for the languages they use.

Changes

Package.swift

• Bump swift-tools-version to 6.1 (required for traits).
• Add 18 traits — one per grammar package — with a .default set enabling all of them, so existing consumers are unaffected.
• Gate each tree-sitter .product(...) with condition: .when(traits: [...]).
• Pin swiftLanguageModes: [.v5] so the tools-version bump doesn't also migrate the package into the Swift 6 language mode (which would turn pre-existing Litext concurrency warnings into hard errors — out of scope here).

CodeHighlighter.swift

• Wrap each import TreeSitterX and its register(...) block in #if <Trait>. Disabled languages are simply never registered; the existing languageConfiguration(for:) nil path already degrades unknown languages to plain text, so no call sites change.

Consumer usage

// Full set — unchanged behavior:
.package(url: "...", from: "x.y.z")

// Only what you need — the rest is never fetched or compiled:
.package(url: "...", from: "x.y.z", traits: ["Swift", "JSON"])

Reviewer notes

• TreeSitterTSX is not a separate product — it ships inside the TreeSitterTypeScript product, so TypeScript + TSX share one TypeScript trait.
• Traits are SwiftPM-only. A consumer adding the package via Xcode's GUI always gets the default (all-languages) set — there is no per-language toggle in the IDE.
• Breaking-ish: minimum build toolchain rises from Swift 5.9 → 6.1.

Verification

• Default build (all languages): Build complete ✓, full test suite passes ✓
• swift build --disable-default-traits --traits Swift,JSON: Build complete ✓, and show-dependencies confirms only tree-sitter-swift + tree-sitter-json remain — the other 16 grammar packages are pruned from the graph.

🤖 Generated with Claude Code

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Project	Deployment	Actions	Updated (UTC)
markdown-view	Ready	Preview, Comment, Open in v0	Jun 20, 2026 10:04pm

[chatgpt-codex-connector]

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[chatgpt-codex-connector]

Update the advertised Swift requirement

Because this tools-version line makes SwiftPM 6.1 the minimum, the README Requirements section still saying Swift 5.9+ is now wrong; users on Swift 5.9 or 5.10 following the published install docs will fail while loading the manifest before they can build. Update the documented minimum/toolchain compatibility along with this manifest change.

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