Add Airtable formula builder tests and update coverage checklist

[qizh]

Summary

• add AirtableFormulaBuilder test suite covering formula composition and apostrophe escaping
• convert TESTS_COVERAGE document to checklist format with statuses and descriptions

Testing

• swift test (fails: SwiftUI module unavailable in this environment)

---

Codex Task

[Copilot]

Pull request overview

This PR adds comprehensive test coverage for the AirtableFormulaBuilder component and restructures the TESTS_COVERAGE.md document from a detailed table format to a more maintainable checklist format with checkboxes tracking implementation status.

Key changes:

• Added AirtableFormulaBuilderTests.swift with three test functions covering formula composition, logical operators (AND/OR/NOT), and apostrophe escaping in string interpolation
• Converted TESTS_COVERAGE.md from nested HTML tables to a markdown checklist format with checkboxes indicating implementation status
• Marked AirtableFormulaBuilder tests as complete in the coverage document

Reviewed changes

Copilot reviewed 2 out of 2 changed files in this pull request and generated 1 comment.

File	Description
Tests/QizhKitTests/AirtableFormulaBuilderTests.swift	New test suite verifying AirtableFormulaBuilder formula generation, logical combinations, and apostrophe escaping functionality
Docs/TESTS_COVERAGE.md	Converted from detailed table format to checklist format with status tracking; marked AirtableFormulaBuilder tests as implemented

[qizh]

@copilot run these tests to see if they succeed

[Copilot]

@qizh I've opened a new pull request, #46, to work on those changes. Once the pull request is ready, I'll request review from you.

[Copilot]

Pull request overview

Copilot reviewed 2 out of 2 changed files in this pull request and generated 1 comment.