[hellofrequencylab]

Firmware half of the phased plan's Phases 0, 3, 5 and 6. The website side goes to frequency-web separately.

What changes

Phase	Firmware
0, board answers	@evt hello {proto, os, fw, commit, board} at the end of boot; system.caps lists every registered command; system.time {epoch} sets the clock from the computer; build.sh stamps the git commit (FW_COMMIT), which system.status and the hello report
3, setup over the cable	frequency.config / frequency.provision {device_id, secret, base?} / frequency.unprovision (new apps/frequency/provision.cpp). The secret is never sent back. Patch 0014 now echoes COMMAND: rpc instead of the whole line, so passwords and secrets stay out of the serial log
5, scans through the cable	With no Wi-Fi, a computer that sent rpc over USB in the last 30 s, and its clock set, the board signs a card tap (HMAC-SHA256 keyed by sha256(secret), the hash frequency-web already stores) and sends it as @evt frequency.scan_relay. The computer posts the exact body with X-Frequency-Device-Id + X-Frequency-Signature, then answers with frequency.relay_reply. The secret never leaves the board. rpc frequency.scan returns the signed scan in its reply instead
6, updates from the website	build.sh writes build/manifest.json (version, commit, app.bin size and sha256, offset 0x10000). New path-filtered workflow .github/workflows/cyberpunkunicorn-os.yml builds on Linux and fails if app.bin outgrows the 0x3C0000 app partition. A cu5k-v<OS_VERSION> tag publishes a release with app.bin, full.bin and the manifest. build.sh's in-place sed now works on GNU sed too

Fixes found along the way: rpc frequency.scan said "queued" when offline but never queued the scan, and sensors.read ended its session twice.

The contract is in apps/remote/PROTOCOL.md, with new sections "Frequency tags", "Setup over the cable", "Scans through the cable", system.caps, system.time and the hello event. BACKEND.md and CLAUDE.md are updated to match.

Verified

• Every changed C++ file passes a syntax check against patched Bruce 1.16.1 with no errors. That is a compile check only; nothing has been linked or run yet. The full patch chain 0001→0015 applies with the regenerated 0014.
• Unlinked objects of the changed files grow by about 15.7 KB. The linked growth should be smaller, since ArduinoJson code is shared, but it hasn't been measured. After cyberpunkunicorn-os: Library for apps whose hardware isn't found yet #9 there is about 330 KB free.
• The new CI workflow is the first full Linux build of this branch. Its result shows on this PR.
• Not tested on hardware yet. That needs a board run: the hello after a reset, system.caps, frequency.provision, then a cable scan once the website accepts the signature headers.

Order

Merge after #9. Both touch apps/remote/app_handlers.cpp: this PR changes the frequency.scan handler, not the LED lines that #9 removes.

🤖 Generated with Claude Code

https://claude.ai/code/session_01AycPrTRVXqSDZhb2NNfyG6