TASK-010: iOS Simulator Support

[michal-blockether]

Problem

agent-browser supports iOS Simulator testing via Appium. spel has viewport/UA emulation but no real mobile browser engine testing.

Real iOS testing catches bugs that emulation cannot: Safari-specific rendering, iOS touch behaviors, platform-specific font rendering, permission dialogs.

Current vs Desired

# agent-browser:
agent-browser -p ios --device "iPhone 15 Pro" open https://example.com
agent-browser -p ios swipe up
agent-browser -p ios tap @e1

# spel:
spel set device "iphone 14" # only viewport + UA emulation

Acceptance Criteria

1. spel --provider ios open https://example.com launches iOS Simulator with Safari
2. spel --provider ios --device "iPhone 15 Pro" open ... targets specific simulator
3. spel --provider ios device list shows available simulators
4. Standard commands work: snapshot, screenshot, click, fill
5. iOS-specific: swipe up/down/left/right, tap @ref
6. Requires Xcode + Appium (documented prerequisites)
7. Graceful error if Xcode/Appium not installed

Type

✨ Feature — Platform expansion

Priority

🟢 P3 — Low. Nice to have, most users fine with viewport emulation.

Effort/Impact

80% effort / 15% impact — Worst ROI (Appium is heavy dependency)

Linear: https://linear.app/blockether/issue/BLO-142