hardware: replace failed Rev B with prototype-ready passive Rev C

[bobberdolle1]

Scope

Replaces the failed/unverified Rev B release path with a canonical Rev C passive RF/energy observation design. Rev B remains archived as non-orderable historical evidence.

Engineering changes

• exact-part ESP32-S3, Ebyte 2.4 GHz/sub-GHz, SAM-M10Q, USB-C, microSD, OLED, power, controls, test points, and antenna interfaces
• native KiCad 10 schematic plus routed four-layer PCB
• PCBA-derived FreeCAD enclosure with fasteners, OLED cradle, plungers, and service envelopes
• exact fitted BOM, placement, Gerbers/drills, PDFs, STEP/STL assemblies, previews, and physical bring-up checklist
• manifest-generated firmware pin contract and canonical PlatformIO target
• reproducible ERC/DRC/mechanical/fabrication/firmware verification plus CI gates
• public README/docs/site capability and maturity corrections; stale router JARs removed

Reproduced evidence

python hardware/verify.py on clean commit aa49c6e:

• KiCad 10.0.5 ERC: 0 errors, 0 warnings
• KiCad 10.0.5 DRC: 0 violations, 0 unconnected pads
• FreeCAD 1.1.3: valid solids, 0 unintended assembly/service collisions
• canonical firmware target: SUCCESS
• clean-source evidence: hardware/rev_c/validation/verification_summary.json

Additional verification:

• all six PlatformIO canonical/legacy profiles built successfully
• host parser suite under ASan/UBSan: 35 passed, 0 failed
• PCB/enclosure/mechanical drawing and rewritten website visually inspected

Maturity

READY FOR FIRST PHYSICAL PROTOTYPE — NOT PRODUCTION VALIDATED.

The fabrication package is limited to one engineering prototype. No assembled, powered, RF-characterized, environmental, field, or regulatory evidence exists yet. Physical validation must follow hardware/rev_c/PROTOTYPE_VALIDATION_CHECKLIST.md.

[bobberdolle1]

CI note: all four checks (build, cad-contracts, parser-tests, static-analysis) failed before running any step. GitHub's job annotation says: “The job was not started because your account is locked due to a billing issue.” This is an account-level Actions blocker, not a test failure. After billing is restored, re-run the failed jobs. The same hardware workflow, all six PlatformIO profiles, and the ASan/UBSan host suite were executed locally; exact results and tool versions are in the PR body and hardware/rev_c/validation/verification_summary.json.