fix(typescript): respect unified js/ts.format settings

[NamesMT]

Problem

Volar's TypeScript formatting service only reads the deprecated per-language format settings (typescript.format.* / javascript.format.*) when formatting embedded script blocks. The unified js/ts.format.* settings are ignored, so a Vue <script setup lang="ts"> block formats differently from a regular .ts file when only the unified settings are configured.

Closes vuejs/language-tools#6150

What VS Code does

VS Code's built-in TypeScript extension reads the unified js/ts.format.* settings first and only falls back to the language-specific sections (typescript.format.* / javascript.format.*) when the unified value is not configured — see readUnifiedConfig.

Change

getFormatCodeSettings now also reads js/ts.format and gives those values precedence over the language-specific sections, while still falling back to the deprecated settings.

One caveat worth noting for reviewers: LanguageServiceEnvironment.getConfiguration only returns resolved values (including registered defaults), with no inspect()-style "was this explicitly set" signal. So we approximate the unified-wins fallback by preferring a unified value only when it differs from its registered default. This behaves identically to VS Code in practice; the only theoretical divergence is explicitly setting a unified key to its exact default while also setting the deprecated counterpart to a different value.

Test plan

Added unit tests covering:

• unified js/ts.format.* settings are honored
• fallback to language-specific typescript.format.* / javascript.format.*
• unified takes precedence when both are set
• defaults are used when nothing is configured