test: add full integration test suite for live API verification

39 tests covering the complete tool surface against a real Webex bot
token. All tests are skipped automatically during normal CI runs and
opt-in via WEBEX_INTEGRATION_TESTS=1 + WEBEX_ACCESS_TOKEN to prevent
unit-test mock interference.

Coverage:
- People: get_webex_me, list_webex_people
- Rooms: full CRUD lifecycle + post-delete GET verification
- Messages: text, markdown, space alias, list, delete
- Adaptive cards: build_webex_adaptive_card, send_webex_adaptive_card
- Memberships: list, response shape, bot-is-moderator assertion
- Space aliases: full create→get→list→update→delete lifecycle
- Teams: list (bots cannot create teams)
- Error handling: structured E-code responses for invalid IDs and
  missing required parameters across all tool categories

Each class manages its own tearDownClass cleanup so resources are
deleted even when individual tests fail.

https://claude.ai/code/session_01Bykkm6kE75wpwuiuL9MHny

Author: claude