add AGENTS.md, update README, fix frame in tcd.c

README.md

@@ -25,8 +25,8 @@ How it works
 ### 1. Signal acquisition
 
 The program opens the file with libavformat, selects the first audio stream,
-decodes up to `--duration` (default 60) seconds of audio, and converts every
-sample to 32-bit float PCM.
+decodes up to `--duration` (default 60) seconds of audio (or the entire file
+when `--full` is used), and converts every sample to 32-bit float PCM.
 
 ### 2. Windowing & FFT
 
@@ -304,6 +304,8 @@ tcd [options] <audio-file>
                         higher = more detections.  Adjust in small steps.
   -f, --fft-size N      FFT size (power of 2) [default: 4096]
   -d, --duration SEC    Max seconds to analyze [default: 60]
+  -r, --recursive       Recurse into subdirectories
+  -F, --full            Analyze entire file (overrides --duration)
   -v, --verbose         Verbose output
   -s, --visual          Graphical spectrum visualization (TUI)
   -V                    Alias for -s