Initial commit: bandsaunter, an RTL-SDR signal scanner

Sweeps any set of frequency ranges, records what it finds, and works out
what kind of signal it was.

- Frequency ranges entered by hand or picked from a 135-entry US band plan,
  including whole-band and all-CW sweeps that resolve the demodulator per
  segment.
- Detection calibrated against the peak-hold detector's own noise statistics,
  so the threshold means real margin over static rather than over the floor.
- A content gate: captures are kept only if they carry voice, decodable CW,
  or an identified digital keying scheme. Speech is recognised by a pitch
  track that drifts, which static cannot imitate.
- Identification of NFM/WFM/AM/SSB, CW with Morse decoded to text, P25, DMR,
  NXDN, D-STAR, POCSAG, FLEX, ACARS, AIS, APRS, n-FSK and n-PSK.
- Gapless streaming capture, with the signal path fast enough to keep up in
  real time, so recordings play back at the right speed.
- Optional one-file-per-frequency recording with spoken timestamps, and
  speech-to-text transcription.
- Menus and command line generated from one settings table, so neither can
  offer something the other cannot; settings persist in ~/.config.

367 tests, run against synthetic signals, a built-in receiver simulator, and
real hardware.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>

pyproject.toml

@@ -0,0 +1,41 @@
+[build-system]
+requires = ["setuptools>=64"]
+build-backend = "setuptools.build_meta"
+
+[project]
+name = "bandsaunter"
+version = "1.0.0"
+description = "Signal scanner, recorder and identifier for RTL-SDR receivers"
+readme = "README.md"
+requires-python = ">=3.10"
+license = {text = "MIT"}
+dependencies = [
+    "numpy>=1.22",
+    "scipy>=1.8",
+    "rich>=12.0",
+    "PyYAML>=5.4",
+]
+
+[project.optional-dependencies]
+plots = ["matplotlib>=3.5"]
+dev = ["pytest>=7.0"]
+# Speech recognition for --transcribe.  Optional: transcription is off by
+# default, and the scan says so plainly when no recogniser is installed.
+transcribe = ["faster-whisper>=1.0"]
+transcribe-small = ["vosk>=0.3"]
+
+# System packages, which pip cannot install.  Recorded here so packaging does
+# not have to rediscover them:
+#   Depends:    librtlsdr0            -- the dongle is unreachable without it
+#   Recommends: espeak-ng             -- clearer spoken timestamps; a built-in
+#                                        synthesiser is used when absent
+
+[project.scripts]
+bandsaunter = "bandsaunter.cli:main"
+
+[tool.setuptools.packages.find]
+include = ["bandsaunter*"]
+
+[tool.pytest.ini_options]
+testpaths = ["tests"]
+filterwarnings = ["ignore::DeprecationWarning"]