Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

Three features: runtime AI backend switching (em ai), Gemini
extra_args support, and cross-dispatcher em catch integration.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

- Add `em ai` runtime backend switching (claude/gemini/none/auto/toggle)
- Add `_em_ai_switch`, `_em_ai_toggle`, `_em_ai_status` functions
- Add `gemini_extra_args` / `claude_extra_args` to _EM_AI_BACKENDS
- Fix `_em_ai_backend_for_op` to read live FLOW_EMAIL_AI env var
- Add `em catch <ID>` email-to-task capture with AI summary + fallback
- Add Ctrl-T=catch fzf keybind in email picker
- Update help text, doctor output, and MASTER-DISPATCHER-GUIDE
- Add 31 tests (22 ai-switch + 9 catch) — all passing

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

- Automated e2e suite (38 tests): file structure, routing, status,
  switch, toggle, extra_args, catch with mocked AI, help, docs, fzf
- Interactive dogfooding suite (14 tests): guided QA with expected
  behavior comparison and judgment logging

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

…+ em catch

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

feat: em ai runtime switching, extra_args, and em catch

- Update v7.2.0 → v7.2.1 across 14 doc files
- Fix em command count 18 → 20 in refcard
- Fix test file count 134 → 137 in CLAUDE.md
- Add [Unreleased] changelog entry for em ai/catch features
- Update .STATUS with merged PR #400

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

Release: v7.3.0 — Email AI Improvements