Expand test suite with conftest, CLI, core gaps, and example smoke te…

[rosspeili]

Description

Expands the test suite for ARPAHLS/aura#2: shared pytest infrastructure, CLI and core-gap coverage, example smoke tests, and coverage reporting in CI.

Added

• tests/conftest.py — shared aura_home, run_aura CLI helper, example runner
• tests/test_cli.py — version, agent CRUD, run, logs, export, export-otel, compare
• tests/test_core_gaps.py — config merge, archive/legacy ids, hash-chain tamper, exporters, runtime, middleware, session modes
• tests/test_examples_smoke.py — all four examples/*/main.py scripts

Updated

• Removed duplicate aura_home fixtures from existing test modules
• CI: pytest --cov=aura --cov-report=term-missing (report only, no gate)
• TESTING.md, CONTRIBUTING.md, CHANGELOG.md

Fixes #2

Type

• Packaging / CI
• Documentation
• CLI (test coverage only)

Checklist

• Linked issue (Fixes #2)
• pytest passes (49 passed, 1 skipped)
• black aura tests — no diff
• flake8 aura tests — clean
• CHANGELOG.md updated under [Unreleased]

Test plan

• pytest — 49 passed, 1 skipped (skillware marker when extra not installed)
• black --check aura tests
• flake8 aura tests
• Example smoke tests run all four example scripts with isolated AURA_HOME