Support source phase imports

[Oleksandr Tarasiuk (a-tarasyuk)]

Fixes #61216

---

This patch adds support for TC39 Source Phase Imports

[Copilot]

Pull request overview

Adds TC39 source-phase import support across parsing, resolution, checking, emit, APIs, and language services.

Changes:

• Supports static import source and dynamic import.source().
• Adds phase-aware resolution, WebAssembly typing, diagnostics, and emit behavior.
• Adds compiler, parser, resolver, API, and fourslash coverage.

Reviewed changes

Copilot reviewed 161 out of 167 changed files in this pull request and generated 1 comment.

Show a summary per file

File	Description
tsc/internal/ast/*	Adds source-phase syntax kinds and AST helpers.
tsc/internal/api/encoder/*	Encodes and decodes the new phase modifier.
tsc/internal/checker/*	Checks syntax and assigns source-module types.
tsc/internal/compiler/*	Tracks phase-aware resolutions and Wasm inputs.
tsc/internal/core/compileroptions.go	Defines supported module modes.
tsc/internal/diagnostics/*	Adds source-import diagnostics.
tsc/internal/fourslash/tests/*sourcePhase*	Tests completions, auto-imports, and organization.
tsc/internal/ls/*	Integrates source imports with language services.
tsc/internal/module/*	Implements phase-aware module resolution and caching.
tsc/internal/parser/*	Parses static and dynamic source imports.
tsc/internal/scanner/*	Recognizes source as a contextual keyword.
tsc/internal/testutil/tsbaseline/js_emit_baseline.go	Includes Wasm files during declaration verification.
tsc/internal/transformers/moduletransforms/commonjsmodule.go	Avoids rewriting import.source() as ordinary dynamic import.
tsc/internal/tspath/extension.go	Adds the Wasm extension.
tools/scripts/tsc/ast.json	Updates AST generation metadata.
packages/typescript/src/*	Exposes the new syntax through the TypeScript API.
tsc/testdata/tests/cases/conformance/importSource/*	Covers syntax, typing, resolution, emit, and errors.
tsc/testdata/baselines/reference/conformance/importSource*	Records expected compiler output.
tsc/testdata/baselines/reference/conformance/importMetaPropertyInvalidInCall.errors.txt	Updates import meta-property suggestions.

Files not reviewed (6)

• tsc/internal/api/encoder/decoder_generated.go: Generated file
• tsc/internal/api/encoder/encoder_generated.go: Generated file
• tsc/internal/ast/ast_generated.go: Generated file
• tsc/internal/ast/kind_generated.go: Generated file
• tsc/internal/ast/kind_stringer_generated.go: Generated file
• tsc/internal/diagnostics/diagnostics_generated.go: Generated file