Add comprehensive formula and rules syntax documentation

[Copilot]

User requested documentation of the formula and validation rule syntax currently used in the ObjectQL project.

Changes

Documentation added:

• docs/guide/formulas-and-rules.md (16KB) - Complete English guide covering formula syntax, validation rules, permission rules, operators, and 50+ examples
• docs/guide/formulas-and-rules-quick-ref.md (5KB) - Condensed syntax reference

Updates:

• VitePress navigation menu - Added new guides under "Data & Logic Layers"
• README.md - Added formula field example and link to syntax guide

Coverage

Formula syntax:

• JavaScript-style expressions with field references
• Arithmetic, string, date operations
• Conditional expressions and lookup references via dot notation
• Special variables: $today, $now, $current_user

# Formula field example
profit_margin:
  type: formula
  expression: "(revenue - cost) / revenue * 100"
  data_type: percent

Validation rules:

• Field-level (required, min/max, pattern)
• Cross-field (compare multiple fields)
• Conditional (apply based on conditions)
• State machine (enforce transitions)
• Business rules (complex constraints)
• Custom (JavaScript functions)

# Cross-field validation example
rules:
  - name: valid_date_range
    type: cross_field
    rule:
      field: end_date
      operator: ">="
      compare_to: start_date
    message: "End date must be after start date"

Operators: Comparison (=, !=, >, >=, <, <=), set membership (in, not_in, contains), logical (all_of, any_of, none_of), special (not_empty, is_null)

All examples verified against actual codebase patterns in /packages/starters/ and /packages/foundation/.

Original prompt

目前项目使用的公式，规则的语法是什么，更新文档给我确认

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[hotlong]

@copilot 我不需要中文文档，我不想维护两套文档

[hotlong]

@copilot 我的意思是删除中文文档，我不需要

[Copilot]

@copilot 我不需要中文文档，我不想维护两套文档

已删除中文文档和总结文件。现在只保留英文文档：

• docs/guide/formulas-and-rules.md
• docs/guide/formulas-and-rules-quick-ref.md

Commit: f3b9c69

[Copilot]

@copilot 我的意思是删除中文文档，我不需要

中文文档已在上一个提交中删除 (f3b9c69)。当前只保留英文文档：

• docs/guide/formulas-and-rules.md
• docs/guide/formulas-and-rules-quick-ref.md

[Copilot]

Pull request overview

This pull request adds comprehensive documentation for formula and validation rule syntax used in the ObjectQL project. The documentation provides English-language guides for defining calculated fields and business rules.

Changes:

• Added complete formulas and rules syntax guide with 50+ examples covering formula syntax, validation rules, permission rules, operators, and best practices
• Added condensed quick reference guide for rapid lookup
• Updated VitePress navigation to include new guides in "Data & Logic Layers" section
• Enhanced README.md with formula field example and link to syntax guide

Reviewed changes

Copilot reviewed 4 out of 4 changed files in this pull request and generated 2 comments.

File	Description
docs/guide/formulas-and-rules.md	Complete 690-line guide covering formula expressions, validation types, permission rules, operators, and best practices with extensive examples
docs/guide/formulas-and-rules-quick-ref.md	270-line condensed syntax reference for quick lookup of common patterns and operators
docs/.vitepress/config.mts	Added navigation menu entries for new guides under "Data & Logic Layers" section with proper indentation
README.md	Added formula field example demonstrating calculated fields and updated feature list to include formulas, with link to new syntax guide