docs: optimize style guide for LLM readers (#1321)

* docs: optimize style guide for LLM readers

Restructure documentation style guide with dependency-first ordering
and LLM-optimized content based on editorial-review-structure analysis.

Key changes:
- Add Universal Formatting Rules section at top (consolidated anti-patterns)
- Move Visual Hierarchy and formatting rules before document types
- Add Document Types decision table for type selection
- Move Before/After example to follow Visual Hierarchy
- Merge Links/Images into single Assets table
- Move tutorial-specific checklist into Tutorial Structure section
- Move Validation Steps to end (submission workflow)
- Cut abstract Quick Principles (no execution value for LLMs)
- Remove emotional/orientation language throughout
- Condense FAQ Sections structure

Result: ~35% reduction (539 deletions, 383 insertions) with improved
parseability for AI agents writing documentation.

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

* docs: clarify explanation checklist admonition limit

Disambiguate 2-3 admonitions max to explicitly show it is a per-document
limit that still respects the universal per-section rule.

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

* docs: clarify header budget vs structure template relationship

Add note explaining that structure templates show content flow, not 1:1
header mapping. Admonitions and inline elements are within sections.

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

* docs: remove horizontal rules to follow own guidelines

Remove all --- section separators to comply with Universal Formatting
Rules. The ## headers provide sufficient visual separation.

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

* docs: address PR review findings for style guide

- Fix forward reference in Header Budget section
- Clarify descriptions rule scope (tables and 5+ item lists)
- Restore realistic FAQ examples
- Add qualifier to admonition content length guideline

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

* docs: further optimize style guide as delta-only document

- Add opener declaring adherence to Google Style Guide and Diataxis
- Remove generic Google style guide sections (Visual Hierarchy patterns,
  Tables constraints, Code Blocks, Lists, Assets)
- Remove Diataxis explainer content (Document Types table, "X documents
  do Y" explanatory sentences, Before/After example)
- Keep all project-specific structure templates and checklists
- Consolidate rules into single Project-Specific Rules table

Result: 367 lines (down from 597), pure delta document assuming
LLM training knowledge of baseline standards.

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

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Co-authored-by: Claude Opus 4.5 <noreply@anthropic.com>

Author: alexeyv