Refactor: Restructure project into pages/ and common/ with co-location convention.

[twoGiants]

Changes

• 🧹 Restructure src/ into src/pages/ (page-specific code with components/ subdirs) and src/common/ (shared services, utils, context, components)
• 🧹 Extract EditToolbar and LeaveModal from FunctionEditPage into separate component files, then fold LeaveModal back into EditToolbar per sub-component rule
• 🎁 Add EditToolbar tests (9 tests covering save flow, error handling, leave modal)
• 🧹 Move all beforeEach/afterEach into describe blocks, merge duplicate beforeEach in OcpClusterService test
• 🧹 Replace runtime import of @patternfly/react-code-editor with import type (fixes Monaco worker bundling)
• 🎁 Add yarn ci script (lint + test + build)
• 🧹 Update init-session command to use yarn ci and handle sandbox failures
• 🧹 Update ARCHITECTURE.md with co-location convention, sub-component rule, hooks directory convention
• 🧹 Update TESTING.md with component vs. page test rules, Vitest/MSW migration, scoping rule
• 🧹 Update WORKFLOW.md startup sequence (drop old step 4, add Jira epic story selection)

[matejvasek]

/lgtm

[matejvasek]

From Claude:

Minor test isolation regression in CreateFunctionForm.test.tsx

The old code had explicit mockClear() calls for the standalone vi.fn() mocks:

// old — describe scope
beforeEach(() => {
  onSubmit.mockClear();
  onCancel.mockClear();
});

The refactor replaced this with just vi.restoreAllMocks() in afterEach, dropping the mockClear() calls. In Vitest v4, vi.restoreAllMocks() only restores spies created with vi.spyOn — it does not clear standalone vi.fn() mocks. So onSubmit and onCancel call history now leaks between tests.

No current test breaks (none assert on call counts), but it's a latent isolation issue. Fix: use vi.clearAllMocks() instead of (or alongside) vi.restoreAllMocks() in the afterEach.