Unify USB connection before installation or recovery

[eirabie]

Summary

USB setup previously asked visitors to choose installation or recovery before checking their speaker. /install/ now starts with one connection action and read-only discovery: recognized OpenAthan opens settings and credential controls; unrecognized firmware opens explicit hardware and erase confirmation with retry, cancel, and troubleshooting.

Connection and recovery remain available without an installation release. Recognized firmware with unreadable status and discovery disconnects cannot authorize flashing. Setup/troubleshooting guides, the installer contract, product/design guidance, and design previews describe the unified flow. Firmware updates remain on the device page or the preserving USB transition.

Area

• Homepage or public documentation
• Hardware/build guidance
• Browser installer
• Project or deployment configuration

Validation

• Relevant routes and links were checked
• User-facing behavior was tested in applicable browsers and viewport sizes
• Accessibility impact was reviewed
• No firmware is compiled by this repository

Automated: formatting/type checks, 111 unit tests, verified v0.4.0 release import, and static build/link/integrity checks passed. Browser validation passed 213 development cases and 171 built-site cases across Chromium, desktop WebKit, and narrow WebKit; three production-only development skips are covered by the built-site run. Desktop and narrow-screen visual review passed.

Physical: not performed for this change. Reference-hardware connection/routing and preservation acceptance remain required before public deployment; simulator checks do not establish hardware qualification.

Licensing and privacy

• No new third-party media or dependency licensing concerns
• No new collection or transmission of user data
• Any licensing, attribution, or privacy impact is documented