Add internal JSDocs throughout the codebase

[Copilot]

Summary

Adds JSDoc comments to all major public APIs across src/server/, src/typescript-generator/, src/repl/, and src/util/. No functional changes.

Original Prompt

Add JSDocs throughout the codebase.

Manual acceptance tests

• Hover over Registry, Dispatcher, ModuleLoader, or ContextRegistry in an IDE — JSDoc tooltip appears with a meaningful description
• Hover over Requirement.select() or Specification.fromFile() — @param and @returns docs are shown
• Hover over RouteBuilder.send() in the repl source — @throws annotations are visible
• Hover over Config interface fields (e.g. alwaysFakeOptionals, buildCache) — inline field docs appear
• No new TypeScript errors or test failures introduced (yarn test passes)

Tasks

• Added class-level JSDoc to all major classes: Registry, ContextRegistry, Dispatcher, ModuleLoader, Transpiler, ModuleTree, ModuleDependencyGraph, ScenarioRegistry, FileDiscovery, Tools, Specification, Requirement, Coder, Script, Repository, OperationCoder, OperationTypeCoder, CodeGenerator, RouteBuilder, RawHttpClient
• Documented all public methods with @param, @returns, and @throws where applicable
• Documented all fields of the Config interface
• Added function-level JSDoc to module-level exports: generate, writeApplyContextType, createResponseBuilder, createKoaApp, koaMiddleware, openapiMiddleware, isProxyEnabledForPath, jsonToXml, determineModuleKind, ensureDirectoryExists, readFile, runtimeCanExecuteErasableTs, escapePathForWindows, startRepl, createRouteFunction
• Fixed a */ sequence inside a JSDoc body (*/* → */*) that caused a parse error
• Added changeset entry (patch)