♻️ Functional decomposition roadmap: Kill the classes, embrace pure functions

[Robdel12]

The Big Picture

We've been refactoring the codebase to be more testable and maintainable using functional decomposition - extracting pure functions from monolithic classes so we can test real behavior with simple input/output assertions.

Status: ✅ Complete

All services have been refactored or deleted:

Service	Status	Notes
TddService	✅	Refactored to src/tdd/ (PR #125)
ApiService	✅	Refactored to src/api/ (PR #127)
build-manager.js	✅	Kept pure functions, deleted class (PR #134)
auth-service.js	✅	Refactored to src/auth/ (PR #129)
config-service.js	✅	Deleted - was thin wrapper (PR #134)
project-service.js	✅	Deleted - was thin wrapper (PR #134)
api-service.js	✅	Deleted - was thin wrapper (PR #134)
server-manager.js	✅	Refactored to src/server-manager/ (PR #133, #134)
test-runner.js	✅	Refactored to src/test-runner/ (PR #133)
screenshot-server.js	✅	Refactored to src/screenshot-server/ (PR #133)
uploader.js	✅	Refactored to functional with DI (PR #133)
html-report-generator.js	✅	Refactored to src/report-generator/ (PR #134)
static-report-generator.js	✅	Uses report-generator module (PR #134)

Key PRs

• PR 🔥 Remove problematic tests causing CI issues #132: Test cleanup (deleted problematic mock-heavy tests)
• PR ♻️ Refactor commands to use functional modules directly #133: Commands refactor to functional modules
• PR 🗑️ Delete unused service wrappers & simplify createServices #134: Services cleanup (deleted thin wrappers, simplified createServices)

The Pattern We Used

For each service:

1. Create a new module (e.g., src/auth/ or src/server-manager/)
2. Extract pure functions into core.js - these need zero mocks to test
3. Create operations with dependency injection in operations.js
4. Write tests with dependency injection - pass stubs as params, not vi.mock
5. Delete thin class wrappers that only forwarded calls
6. Delete mock-heavy tests - replaced with proper unit tests

Results

• ✅ No vi.mock in new tests
• ✅ Pure functions tested with input/output assertions
• ✅ Dependency injection for anything with I/O
• ✅ Net reduction in test code (less mocking boilerplate)
• ✅ Commands use functional modules directly
• ✅ createServices() simplified to only what plugins need

What's Left in src/services/

Only services that provide plugin API or need EventEmitter:

• ServerManager class - plugins use EventEmitter interface
• TestRunner class - plugins use EventEmitter interface
• Pure functions in build-manager.js, uploader.js

These are documented as the public plugin API.

[Robdel12]

🎉 All functional decomposition work complete! See issue body for full summary of changes across PRs #132, #133, and #134.