v0.1.3 - Stable USB rate and repeated-copy recovery

Improves transfer integrity and weak-packet recovery without adding receiver hardware.

• New firmware starts at 1,000,000 baud and advertises rate negotiation. The host switches to 500,000 baud after an old-rate ACK, verifies the new rate, and retains legacy compatibility.
• If single-copy decoding fails, the decoder can combine measured symbol evidence from correctly spaced, closely matching repeated copies. Timing/grouping is selected before payload checks. Exact header, additive checksum, and paired-counter checks remain required; no checksum-directed bit flipping is used.
• Readings record recovery_method and repetition_count; dashboard receiver settings show the negotiated rate. Includes measured regression and fresh holdout/control fixtures.

Validation: 21 local host/dashboard tests and GitHub Actions host/ESP32 build passed. A 20-full-frame stress test at 500,000 baud had zero CRC/framing errors. A separate fresh four-burst test decoded all four bursts with zero transfers lost; four between-burst controls yielded no accepted payload. Two of the four bursts required repetition combining.

The normal dashboard subsequently received 6 fresh packets in 10 capture windows with zero CRC/framing errors, including repeated-copy recoveries. Latest checked reading was 17.5 C / 63.5 F, 90% RH, station 14AB. These are short bench observations, not a controlled long-term success-rate comparison. Some bursts still fail. RF tuning accuracy, harmonic origin, native 915 MHz reception, and useful range remain unverified.