Enable verbatimModuleSyntax for eng scripts

[timotheeguerin]

Type-only imports in typespec-azure are still emitted as runtime imports. That leaves dead runtime edges in the emitted JS, makes module side effects ambiguous, and blocks ever turning verbatimModuleSyntax on repo-wide — something core has already been rolling out package by package.

This enables the flag for the eng/ scripts (tsconfig.eng.json) and rewrites the imports it flags:

-import { SdkContext } from "./interfaces.js";
+import type { SdkContext } from "./interfaces.js";

The rewrite was driven by the compiler rather than by regex: build the program with the flag on, collect the TS1484/TS1485/TS1205 diagnostics, and change exactly the specifiers TypeScript names — hoisting to import type when every specifier in a clause is type-only, otherwise adding an inline type modifier. tsc then reports zero new errors against a pre-change baseline, so no value binding was turned into a type-only one.

One of a series of PRs, one per package, so each diff stays reviewable. They are independent and can land in any order.

PR	Scope
#5127	samples, typespec-python, benchmark, typespec-azure-playground-website, typespec-metadata, spector-runner
#5128	azure-http-specs
#5129	typespec-autorest
#5130	typespec-azure-core
#5131	typespec-azure-resource-manager
#5132	typespec-client-generator-core
#5133	typespec-go
#5134	typespec-ts
#5135	eng/ scripts

typespec-autorest-canonical, typespec-azure-portal-core and typespec-azure-rulesets already had the flag. typespec-java is deliberately left out: its src/ is copied in at build time from azure-sdk-for-java, so the flag would break its build until those sources are migrated upstream.

Once these land, a follow-up will hoist the flag into a repo-level tsconfig.base.json and drop the per-package copies, so new packages inherit it by default.

[github-actions]

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[azure-sdk-automation]

You can try these changes here

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