Test suite improvements

[cassieemb]

Summary

Several independent test-quality improvements: tighten assertions/structure, and add a shared helper that centralizes setup. Items 1–4 can be done à la carte; item 5 (the helper) is the foundational structural change.

Directive

1. Magic wire strings → constants: tests/relay/call_test.rb, tests/relay/message_test.rb already require the relay constants but assert raw strings ('calling.answer', 'answered', 'queued'/'sent'/'delivered'). Use the defined constants.
2. De-dup skill lists: tests/skills_test.rb and tests/registry_test.rb repeat an identical ~18-element skill list — have both consume one shared constant. Leave the independent copy in tests/skill_name_test.rb (it's a deliberate cross-check).
3. Strengthen weak assertions: replace presence-only checks (e.g. assert tools[0].key?(:datamap), assert(result.key?('sid') || result.key?('name'))) with exact value/shape assertions (tests/skills/weather_api_skill_test.rb, tests/rest/compat_calls_streams_mock_test.rb).
4. Split inline multi-path tests: one method exercises several input paths inline (tests/skills/web_search_skill_test.rb, weather_api_skill_test.rb, datasphere_skill_test.rb) — split so a failure pinpoints the path.
5. Add a shared tests/test_helper.rb: there's no central helper, so global-state reset (skill registry, ENV) and the WEBrick/ephemeral-port + skill-fixture setup are duplicated across tests/cli_test.rb, tests/per_skill_parity_test.rb, and the skill tests — leaving an ENV/registry leakage window. Centralize global-state reset and the shared fixtures in tests/test_helper.rb; have test files require it.

Guardrails

The test_helper refactor (item 5) must not change what any test asserts — only where setup lives. Items 1 & 3 intentionally change assertions (to be stricter/exact).

Acceptance

• no raw wire strings where a constant exists
• one canonical skill list (plus the intentional cross-check)
• no presence-only assertions on known values
• each input path is its own test
• shared tests/test_helper.rb exists; duplicated setup removed
• suite green and order-independent (rake test and a shuffled run)

Verify

rake test; run twice to check for order dependence.