feat: add contract coverage analysis

[iammrjude]

Description

Adds Soroban contract coverage analysis for StarForge test runs, including function coverage, branch-path tracking, line-span coverage, coverage goals, report generation, visualization data, and CI workflow generation.

Closes #367

Type of Change

• Bug fix
• New feature
• Breaking change
• Documentation update

Changes Made

• Expanded contract coverage analysis with function, line, and branch coverage tracking
• Added branch detection for if, match, auth checks, assertions, and result propagation paths
• Added coverage goals for overall, function, line, and branch coverage
• Added HTML, JSON, Markdown, and text coverage report rendering
• Added coverage visualization data for summary bars and function heatmaps
• Added starforge test coverage flags for reports, thresholds, CI mode, and GitHub Actions workflow generation
• Integrated coverage metadata into existing test runner and contract fixture framework
• Added focused integration tests for coverage tracking, reporting, goals, and CI workflow output
• Updated command reference documentation

Testing

How has this been tested?

Ran targeted validation before the final master sync:

• Unit tests added/updated
• Integration tests added/updated
• Manual testing performed

cargo check
cargo fmt --all -- --check
cargo clippy -- -D warnings
cargo test --test contract_coverage_analysis -- --nocapture
cargo test --test contract_testing_automation -- --nocapture
cargo test --test contract_testing_framework -- --nocapture

Test Coverage

• Happy path: coverage report tracks covered Soroban contract functions
• Edge cases: uncovered functions, partial branch coverage, and missed thresholds
• Error handling: CI mode fails when configured coverage goals are not met

Code Quality Checklist

• My code follows the style guidelines of this project (cargo fmt)
• I have performed a self-review of my own code
• I have made corresponding changes to the documentation
• I have added tests that prove my feature works

Breaking Changes

None.

Documentation

• README.md updated
• DEVELOPER_GUIDE.md updated
• API_REFERENCE.md updated
• Command reference updated

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You can now already apply to more issues while waiting for a review of this PR. Keep up the great work! 🚀

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