[chore](trx-rs): remove unused external ft8_lib

Delete the obsolete ft8_lib submodule and update documentation to point at the pure Rust trx-ftx decoder.

Co-authored-by: OpenAI Codex <codex@openai.com>
Signed-off-by: Stan Grams <sjg@haxx.space>

.gitmodules

@@ -5,6 +5,3 @@
 [submodule "docs"]
 	path = docs
 	url = http://github.com/sgrams/trx-rs.wiki.git
-[submodule "external/ft8_lib"]
-	path = external/ft8_lib
-	url = ssh://git@github.com/sgrams/ft8_lib.git

CLAUDE.md

@@ -54,7 +54,7 @@ src/
   decoders/
     trx-aprs/         # APRS packet decoder
     trx-cw/           # CW (Morse) decoder
-    trx-ft8/          # FT8 decoder (wraps external ft8_lib C library)
+    trx-ftx/          # Pure Rust FTx decoder (FT8/FT4/FT2)
     trx-wspr/         # WSPR decoder
     trx-decode-log/   # Shared decoder logging (JSON Lines, date-rotated files)
 ```
@@ -86,7 +86,7 @@ The rig controller (`src/trx-core/src/rig/controller/`) is the central state man
 
 ### Decoders
 
-Signal decoders run as background tasks in `trx-server`, consuming decoded audio. `trx-ft8` wraps a C library (`external/ft8_lib`). Decoded frames can be forwarded to PSKReporter and APRS-IS (IGate) uplinks, or logged via `trx-decode-log`.
+Signal decoders run as background tasks in `trx-server`, consuming decoded audio. `trx-ftx` provides the FT8/FT4/FT2 decoder in pure Rust. Decoded frames can be forwarded to PSKReporter and APRS-IS (IGate) uplinks, or logged via `trx-decode-log`.
 
 ### Plugin system
 

OVERVIEW.md

@@ -52,7 +52,7 @@ Target users are amateur radio operators who want networked, automated, or multi
 | CAT serial | tokio-serial |
 | CLI | clap |
 | Logging | tracing / tracing-subscriber |
-| FT8 decode | ft8_lib (external C library via FFI) |
+| FTx decode | trx-ftx (pure Rust) |
 
 ---
 
@@ -144,7 +144,7 @@ trx-rs/                          # Workspace root
     └── decoders/
         ├── trx-aprs/            # APRS packet decoder
         ├── trx-cw/              # CW / Morse decoder
-        ├── trx-ft8/             # FT8 decoder (wraps ft8_lib C library)
+        ├── trx-ftx/             # Pure Rust FTx decoder (FT8/FT4/FT2)
         ├── trx-wspr/            # WSPR beacon decoder
         ├── trx-rds/             # FM RDS decoder
         └── trx-decode-log/      # JSON Lines log rotation for decoded frames
@@ -704,7 +704,7 @@ All decoders run as background Tokio tasks inside `trx-server`. They subscribe t
 |-------|---------|-------|
 | `trx-aprs` | APRS (AX.25) | Forwards to APRS-IS if enabled |
 | `trx-cw` | CW / Morse | Auto WPM detection |
-| `trx-ft8` | FT8 | Wraps `external/ft8_lib` C library via FFI; posts to PSKReporter |
+| `trx-ftx` | FTx | Pure Rust FT8/FT4/FT2 decoder; posts to PSKReporter |
 | `trx-wspr` | WSPR beacons | Posts to PSKReporter |
 | `trx-rds` | FM RDS | Station name, radiotext, time |
 | `trx-decode-log` | Logging infrastructure | JSON Lines, date-rotated files |

src/decoders/trx-ftx/FTX_CRATE.md

@@ -2,9 +2,9 @@
 
 ## Goal
 
-Replace `trx-ft8` (C FFI wrapper around ft8_lib + custom FT2 code) with a pure Rust
+`trx-ftx` is the pure Rust replacement for the old `trx-ft8` C FFI wrapper.
-implementation. The new `trx-ftx` crate provides the exact same public API
+It provides the same public API (`Ft8Decoder`, `Ft8DecodeResult`) so it can
-(`Ft8Decoder`, `Ft8DecodeResult`) so it is a drop-in replacement.
+serve as a drop-in decoder implementation.
 
 ## Why
 
@@ -85,21 +85,22 @@ hound = "3"             # WAV file reading for integration tests
 ### Phase 5: Migration
 14. Convert `trx-ft8` to thin re-export of `trx-ftx`
 15. Delete C sources: `ft8_wrapper.c`, `ft2_ldpc.c`, `build.rs`
+16. Remove the vendored `ft8_lib` checkout after the port is complete
 
-## C Sources Being Ported
+## Historical C Sources Ported
 
 | C Source | Rust Target | Lines |
 |----------|-------------|-------|
-| `external/ft8_lib/ft8/message.c` | `message.rs` | 1156 |
+| `ft8_lib/ft8/message.c` | `message.rs` | 1156 |
 | `src/decoders/trx-ft8/src/ft8_wrapper.c` | `decoder.rs` + `ft2/` | 1800 |
-| `external/ft8_lib/ft8/decode.c` | `decode.rs` | 773 |
+| `ft8_lib/ft8/decode.c` | `decode.rs` | 773 |
-| `external/ft8_lib/ft8/constants.c` | `constants.rs` | 391 |
+| `ft8_lib/ft8/constants.c` | `constants.rs` | 391 |
-| `external/ft8_lib/ft8/text.c` | `text.rs` | 303 |
+| `ft8_lib/ft8/text.c` | `text.rs` | 303 |
-| `external/ft8_lib/common/monitor.c` | `monitor.rs` | 261 |
+| `ft8_lib/common/monitor.c` | `monitor.rs` | 261 |
-| `external/ft8_lib/ft8/ldpc.c` | `ldpc.rs` | 251 |
+| `ft8_lib/ft8/ldpc.c` | `ldpc.rs` | 251 |
-| `external/ft8_lib/ft8/encode.c` | `encode.rs` | 200 |
+| `ft8_lib/ft8/encode.c` | `encode.rs` | 200 |
-| `external/ft8_lib/ft8/crc.c` | `crc.rs` | 63 |
+| `ft8_lib/ft8/crc.c` | `crc.rs` | 63 |
-| `external/ft8_lib/fft/*.c` | replaced by `rustfft` | 555 |
+| `ft8_lib/fft/*.c` | replaced by `rustfft` | 555 |
 
 ## Public API (matches trx-ft8 exactly)
 
@@ -129,5 +130,5 @@ impl Ft8Decoder {
 ## Testing Strategy
 
 - Unit tests per module: CRC round-trip, LDPC recovery, message pack/unpack
-- Integration tests: decode WAV files from `external/ft8_lib/test/wav/`
+- Integration tests: decode reference WAV fixtures when available
 - Compatibility test: `ft2_uses_distinct_block_size` (FT4=576, FT2=288, window=45000)