v2.5.1 - HT STBC Multi-Antenna Router Fix

[francescopace]

Fixed

• ESP32-C5/C6 STBC multi-antenna router fix: Multi-antenna routers with STBC TX send two HT training fields per frame (HT-LTF1 + HT-LTF2), causing the CSI callback to receive 256-byte packets instead of the expected 128 bytes for HT20. On ESP32-C5/C6, wifi_csi_acquire_config_t has no field to disable HT STBC capture (unlike older chips). ESPectre now accepts these packets and takes the first 64 subcarriers (HT-LTF1), which is a valid channel estimate ([BUG] ESP32-C6: All CSI packets filtered — 256-byte packets rejected by HT20 128-byte check #76, Difference in CSI Data Length (AEGHB-1257) espressif/esp-csi#238)
• Micro-ESPectre NBVI calibration on ESP32-C3: Fixed OOM crashes during calibration caused by large in-memory allocations in the streaming NBVI computation phase; calibration now completes successfully on C3 with ~59 KB free heap
• ESPHome 2026.2.0+ compatibility: Ensure SPIFFS inclusion for newer ESPHome versions (fix: ensure spiffs inclusion for ESPHome 2026.2.0+ compatibility #87)
• CI develop branch: Use local component configs instead of main branch for CI builds on develop

Changed

• Micro-ESPectre NBVI calibration speed: Packet collection rate improved ~3x on ESP32-C3 (28 → 80 pps) by skipping sqrt on guard band subcarriers (excluded from NBVI selection), caching math.sqrt locally, and using integer arithmetic in the magnitude loop

Added

• Performance documentation: RAM, Flash, and detection timing benchmarks for ESP32-C3 and ESP32-C6 in PERFORMANCE.md
• Performance logging: Lightweight DEBUG-level logging for heap usage (startup/post-calibration) and detection time (~10s interval)
• git_ref substitution: All example YAML files now use a git_ref substitution, making it easy to switch between branches, tags, or commits
• Snapshot builds: Automated pre-release builds on every push to main, providing pre-compiled firmware for testing fixes before official releases

Documentation

• Clarify that NBVI calibration applies only to MVS mode
• Add media section in README

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This discussion was created from the release v2.5.1 - HT STBC Multi-Antenna Router Fix.