chore: upgrade TypeScript to 7.0.2

[Copilot]

TypeScript 7 drops the JavaScript Compiler API from the main typescript package — ts.sys, ts.createProgram, ts.SyntaxKind, etc. are gone. Tools still needing it must use the @typescript/typescript6 compatibility package.

Version changes

• typescript catalog: ~6.0.2 → ~7.0.2
• http-client-python, http-client-csharp: updated independently (excluded from workspace)
• vite-plugin-dts: 5.0.2 → 5.0.3 (first version with TS7 support)

TypeScript Compiler API compatibility

Added @typescript/typescript6: ~6.0.2 to the catalog. Packages using vite-plugin-dts (html-program-viewer, playground, playground-website, react-components, spec-dashboard) now declare it as a devDep.

Type error fixes (TS7 stricter inference)

TS7's bidirectional inference now narrows R to false instead of boolean in onRequest overloads:

• compiler/src/server/server.ts: connection.onRequest<boolean, unknown>(...)
• typespec-vscode/src/tsp-language-client.ts: lc.onRequest<string | undefined, unknown>(...)

pnpm patches for third-party packages using the Compiler API

Package	What was patched
@alloy-js/cli@0.24.0	typescript → @typescript/typescript6 in build.js / typescript.js
typedoc@0.28.19	All from "typescript" → from "@typescript/typescript6" (25+ files)
@astrojs/check@0.9.9	require.resolve('typescript') → require.resolve('@typescript/typescript6')
@astrojs/language-server@2.16.10	require('typescript') → require('@typescript/typescript6') in check.js

Each patched package also gets @typescript/typescript6 injected via packageExtensions in pnpm-workspace.yaml.

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