Build Orchestrator API

[Isabel Duan (iisaduan)]

3B of #63875

full description in progress

This PR implements what, in TS<6, was called the SolutionBuilder. In TS7.1, it will now be called the BuildOrchestrator.

class BuildOrchestrator {
    async build(project?: string): Promise<number>
    async buildReferences(project: string): Promise<number> 
    async clean(project?: string): Promise<number> 
    async cleanReferences(project?: string): Promise<number>
}

Usage example:

const orchestrator = await api.createBuildOrchestrator(
        { cwd: "/", fs },
        ["/c/tsconfig.json"],
         commandLineOptions,
);
orchestrator.build()

notes:

• the API client serves as what used to be the SolutionBuilderHost, so no need to create and pass an extra host
• no distinction between a SolutionBuilder and SolutionBuilderWithWatch, both modes can be used through CreateBuildOrchestrator(), and you can activate watch by creating with watch options.

[Copilot]

🟡 Changes recommended

Host routing, configuration refresh, watch lifecycle, and clean-result handling contain blocking correctness issues.

Once you've addressed the issues Copilot identified, you can request another Copilot review.

Pull request overview

Adds the Build Orchestrator API for building and cleaning project graphs through sync and async clients.

Changes:

• Adds selective build, reference-build, clean, and reference-clean operations.
• Exposes orchestration through the API protocol and clients.
• Adds virtual filesystem deletion support and integration tests.

File summaries

File	Description
tsc/internal/project/session.go	Exposes the default library path.
tsc/internal/execute/build/orchestrator.go	Implements reusable build and clean orchestration.
tsc/internal/execute/build/clean_test.go	Tests server-side cleaning behavior.
tsc/internal/api/session.go	Handles Build Orchestrator API requests.
tsc/internal/api/proto.go	Defines orchestration protocol types.
tsc/internal/api/callbackfs.go	Adds delegated file removal.
packages/typescript/src/api/async/api.ts	Adds the asynchronous client API.
packages/typescript/src/api/sync/api.ts	Adds the generated synchronous client API.
packages/typescript/src/api/proto.generated.ts	Adds generated protocol declarations.
packages/typescript/src/api/fs.ts	Exposes the removeFile callback.
packages/typescript/test/async/api.test.ts	Tests asynchronous orchestration.
packages/typescript/test/sync/api.test.ts	Tests synchronous orchestration.

Review details

• Files reviewed: 12/12 changed files
• Comments generated: 12
• Review effort level: Balanced

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