feat: core framework modules (session, collector, logger, reporter)

[kristopherjturner]

Overview

Build out the core framework modules under src/core/ that all tool integrations depend on: session management, result collection, logging, and reporting interfaces.

Scope

• src/core/session.py — Test session lifecycle (init, run, teardown)
• src/core/collector.py — Unified result collection interface
• src/core/logger.py — Structured logging with configurable outputs (console, file, Azure Monitor)
• src/core/reporter.py — Base class for report format plugins (JSON, CSV, HTML)
• Unit tests for all core modules

Acceptance Criteria

• All tool integrations use core session/collector/logger interfaces (no duplication)
• Session state is persisted to state/ for crash recovery
• Structured log output is compatible with Azure Monitor / Log Analytics ingestion
• Unit test coverage ≥80% for src/core/

Dependencies

• Parent Epic: [Epic] Load Testing Toolkit Full Build-Out #8
• Config & schema: feat: config & schema expansion for all load test profiles #9