Hierarchy nested client support

[qiaozha]

fixes #2887
fixes #2612

implementation of the hierarchy nested clients. See design doc here

[Copilot]

Pull Request Overview

This PR implements hierarchical nested client support across the TypeSpec-TS generator, filtering out individually-initialized children where appropriate and threading a [hierarchy, client] tuple (clientMap) through modular codegen helpers.

• Introduces InitializedByFlags filtering in getMethodHierarchiesMap and a new getClientHierarchyMap utility.
• Updates getModularClientOptions to accept the [hierarchy, client] tuple and adjust subfolder logic.
• Refactors all modular emit and build helpers (e.g., operations, subpath indices, client context) to use the new tuple signature.
• Adds a nested-client test configuration and spec under packages/typespec-test.

Reviewed Changes

Copilot reviewed 62 out of 63 changed files in this pull request and generated 2 comments.

Show a summary per file

File	Description
packages/typespec-ts/src/utils/operationUtil.ts	Filter out individually initialized nested clients in method queue
packages/typespec-ts/src/utils/clientUtils.ts	Added getClientHierarchyMap, updated getModularClientOptions
packages/typespec-ts/src/modular/*	Propagate [hierarchy, client] through emit/build helper signatures
packages/typespec-ts/src/index.ts	Switch emitter flow to iterate getClientHierarchyMap tuples
packages/typespec-test/test/nestedClient/*	Add nested client test config and TypeSpec spec
.vscode/settings.json	Add formatting settings for TypeSpec files

Files not reviewed (1)

• common/config/rush/pnpm-lock.yaml: Language not supported

Comments suppressed due to low confidence (3)

packages/typespec-ts/src/utils/operationUtil.ts:568

• [nitpick] The filtering logic for child clients based on InitializedByFlags.Individually is duplicated later in this function. Extract it into a helper (e.g., getNonIndependentChildren) to reduce duplication and improve readability.

client.children?.filter((p) => {

packages/typespec-ts/src/modular/buildProjectFiles.ts:38

• [nitpick] Destructure the tuple directly for clarity. For example:

for (const [hierarchy, client] of clientMap) {
  // use `client` directly
}

for (const flattenedClient of clientMap) {

packages/typespec-test/test/nestedClient/spec/main.tsp:1

• You’ve added a nested client spec, but there’s no assertion or test verifying the actual generated code for nested clients. Consider adding an end-to-end test that inspects the generated folder structure and client hierarchy to catch any regressions.

import "@typespec/http";

[MaryGao]

Approved and please resolve any left small comments!