[docs](trx-rs): generate the example config and correct the manual

trx-rs.toml.example was maintained by hand and had fallen well behind: no
[[rigs]], no [[remotes]], no [timeouts], no bandplan or decode-history
settings, and a [frontends.http].default_rig_id that had been renamed.

Generate it from the config structs instead, so a new field shows up the moment
it exists, and add a test that fails when the checked-in copy drifts:

    cargo run -p trx-config --example generate_example

Section comments come from a small table; a section without an entry is still
emitted, so forgetting a comment can never drop a setting from the example.

The manual was wrong about the basics.  It listed five config search paths, none
of which the loader has ever looked at (the real order is ./trx-rs.toml → XDG →
/etc), called --print-config output "fully commented" when it carries no
comments at all, and documented a TRX_PLUGIN_DIRS variable no code reads.  It
also still described [frontends.rigctl].port as the bind port years after
rig_ports replaced it.  Fixed, and the new configuration features are written
up alongside.

Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01SyX26FCpMQxiBoC7r5K1A7
Signed-off-by: Stan Grams <sjg@haxx.space>

README.md

@@ -93,13 +93,17 @@ The wizard walks you through rig selection, serial port detection, audio
 settings, and frontend options, then writes `trx-server.toml` and
 `trx-client.toml`.
 
-Alternatively, generate example configs and edit them by hand:
+Alternatively, copy `trx-rs.toml.example` — a commented example covering every
+setting — and edit it by hand:
 
 ```bash
-./target/release/trx-server --print-config > trx-server.toml
-./target/release/trx-client --print-config > trx-client.toml
+cp trx-rs.toml.example trx-rs.toml
+./target/release/trx-server --check-config --config trx-rs.toml
 ```
 
+`--check-config` reports everything wrong with a config without starting
+anything. `--print-config` prints the same settings without comments.
+
 ### 4. Run
 
 ```bash
@@ -107,6 +111,9 @@ Alternatively, generate example configs and edit them by hand:
 ./target/release/trx-client --config trx-client.toml
 ```
 
+A single `trx-rs.toml` can configure both: the server reads its `[trx-server]`
+section and the client reads `[trx-client]`.
+
 Open the configured HTTP frontend address in a browser (default `http://localhost:8080`).
 
 ## How It Works