Remove `.astro-builder/style-guide.md` from astro-builder init

[pcamarajr]

Remove .astro-builder/style-guide.md from astro-builder init

Type: feature / scope clarification
Plugin: astro-builder

Problem

astro-builder currently generates .astro-builder/style-guide.md during /astro-builder:init (voice, tone, writing conventions) alongside technical artifacts. That mixes editorial concerns with Astro engineering (architecture, collections, design tokens, anti-patterns).

Prose style belongs with content-ops (e.g. /init style, configured guidelines). Keeping a writing guide in astro-builder duplicates responsibility and confuses the plugin boundary.

Expected outcome

• /astro-builder:init does not create style-guide.md under .astro-builder/ and does not ship docs/init-templates/style-guide.md.template.
• Generated CLAUDE.md template — remove the bullet that points to .astro-builder/style-guide.md.
• README “What gets generated by /init” — drop style-guide.md from the tree.
• astro-builder agent — remove style-guide.md from the mandatory pre-read list.
• /astro-builder:translate — do not require or cite .astro-builder/style-guide.md; infer tone from source copy and existing content in the target locale (and CLAUDE.md for project context only).
• /astro-builder:audit — remove the style-guide audit step and any dependency on .astro-builder/style-guide.md; adjust skill description if it mentions “style guide violations” for prose.

Out of scope

• Replacing prose style enforcement elsewhere (content-ops remains the home for style guides).
• Changing design-system.md (implementation-level tokens/patterns) unless a separate issue calls for it.

Acceptance criteria

• No references to .astro-builder/style-guide.md in astro-builder init output, templates, README, agents, translate, or audit skills.
• Existing projects that already have the file are untouched by this change (optional one-line note in README that the file is legacy/deprecated if teams want to delete it manually — only if you decide to document migration).