[feat](trx-rs): redesign SDR noise blanker with tuning profiles

The old IQ noise blanker tracked a fast running RMS and, on a
threshold crossing, replaced the sample with the last clean one. That
hard sample-and-hold is a step discontinuity: it splatters energy back
across the wideband passband, so after the narrow channel filter it
often sounded worse than the noise it removed — especially on SSB, CW
and digital. It also had no look-ahead (the impulse leading edge leaked
through before the fast RMS reacted), blanked only single samples, and
used a fixed 1/128 time constant that did not scale with capture rate.

Redesign the blanker around accepted wideband-NB practice and add
profiles matched to the interference source:

- Noise-floor tracker updated only from clean samples and frozen while
  blanking, so a burst cannot desensitise detection.
- Detection on instantaneous power vs threshold² × noise floor.
- Look-ahead delay line so the gate closes *before* the impulse reaches
  the output, removing the leading edge.
- Raised-cosine tapered gate (ramp 1→0→1) instead of a hard hold, which
  minimises blanker splatter.
- Windowed blanking that re-arms on every detected sample to cover the
  full width of a burst.
- All timings expressed in real time and converted to samples at the
  capture rate, so behaviour is consistent across SDR sample rates.

Profiles (`NoiseBlankerProfile`, default `spike`): spike, ignition,
powerline, broadband — each selects the blank window, look-ahead, taper
and floor time constant. `threshold` stays orthogonal as the
sensitivity knob.

Core/protocol:
- New `NoiseBlankerProfile` in trx-core (serde/parse/u8/TS), re-exported
  at the crate root; `RigFilterState.sdr_nb_profile` for state sync.
- `profile` added to `RigCommand`/`ClientCommand::SetSdrNoiseBlanker`,
  the trait method, and the command mapping.

Config: `[rig.sdr.noise_blanker] profile = "spike"` (regenerated
trx-rs.toml.example).

SDR backend: `NoiseBlanker` rewritten in the channel DSP; profile wired
through `SoapySdrConfig`, the runtime setter, and `filter_state()`.

Frontend: an "NB profile" selector in the SDR advanced controls
(POST /set_sdr_noise_blanker&profile=…), reflecting server state; the
profile rides along with the enable/threshold quick toggle so it is
preserved. Regenerated generated.ts and app.js.

Tests: profile u8/parse round-trips (trx-core); DSP tests for impulse
suppression with no leading-edge leak, strong-steady-signal
pass-through, and wider-profile-blanks-longer.

Docs: User-Manual NB section rewritten for the new algorithm and
profiles.

Signed-off-by: Stan Grams <sjg@haxx.space>

src/trx-client/trx-frontend/trx-frontend-http/assets/web/generated/app.js

@@ -4766,6 +4766,13 @@ function render(update) {
           sdrNbThresholdEl.value = String(Math.round(update.filter.sdr_nb_threshold));
         }
       }
+      if (typeof update.filter.sdr_nb_profile === "string") {
+        sdrNbProfile = update.filter.sdr_nb_profile;
+        if (sdrNbProfileWrapEl) sdrNbProfileWrapEl.style.display = "";
+        if (sdrNbProfileEl && document.activeElement !== sdrNbProfileEl) {
+          sdrNbProfileEl.value = update.filter.sdr_nb_profile;
+        }
+      }
     }
     if (typeof update.filter.sdr_dig_sideband === "string") {
       sdrDigSidebandSupported = true;
@@ -6644,7 +6651,10 @@ var sdrNbEnabledEl = document.getElementById("sdr-nb-enabled");
 var sdrNbThresholdControlsEl = document.getElementById("sdr-nb-threshold-controls");
 var sdrNbThresholdEl = document.getElementById("sdr-nb-threshold");
 var sdrNbThresholdSetBtn = document.getElementById("sdr-nb-threshold-set");
+var sdrNbProfileWrapEl = document.getElementById("sdr-nb-profile-wrap");
+var sdrNbProfileEl = document.getElementById("sdr-nb-profile");
 var sdrNbSupported = false;
+var sdrNbProfile = "spike";
 var sdrDigSidebandWrapEl = document.getElementById("sdr-dig-sideband-wrap");
 var sdrDigSidebandEl = document.getElementById("sdr-dig-sideband");
 var sdrDigSidebandSupported = false;
@@ -7019,7 +7029,7 @@ function submitSdrNbState() {
   const threshold = sdrNbThresholdEl ? Number.parseFloat(sdrNbThresholdEl.value) : 10;
   if (!isFiniteNumber(threshold) || threshold < 1 || threshold > 100) return;
   postPath(
-    `/set_sdr_noise_blanker?enabled=${enabled ? "true" : "false"}&threshold=${encodeURIComponent(threshold)}`
+    `/set_sdr_noise_blanker?enabled=${enabled ? "true" : "false"}&threshold=${encodeURIComponent(threshold)}&profile=${encodeURIComponent(sdrNbProfile)}`
   ).catch(() => {
   });
 }
@@ -7028,6 +7038,16 @@ if (sdrNbEnabledEl) {
     submitSdrNbState();
   });
 }
+if (sdrNbProfileEl) {
+  sdrNbProfileEl.addEventListener("change", () => {
+    const profile = sdrNbProfileEl.value || "spike";
+    if (profile !== "spike" && profile !== "ignition" && profile !== "powerline" && profile !== "broadband") {
+      return;
+    }
+    sdrNbProfile = profile;
+    submitSdrNbState();
+  });
+}
 function submitSdrNbThreshold() {
   if (!sdrNbThresholdEl) return;
   const parsed = Number.parseFloat(sdrNbThresholdEl.value);

src/trx-client/trx-frontend/trx-frontend-http/assets/web/index.html

@@ -385,6 +385,15 @@ SPDX-License-Identifier: GPL-2.0-or-later
                   </label>
                   <button id="sdr-nb-threshold-set" type="button" class="wfm-inline-btn">Set</button>
                 </div>
+                <label class="wfm-control" id="sdr-nb-profile-wrap" style="display:none;">
+                  <span class="wfm-control-label" title="Matches the blanker to the interference: Spike = sharp bursts, Ignition = engine/PWM, Powerline = mains buzz, Broadband = dense noise.">NB profile</span>
+                  <select id="sdr-nb-profile" class="status-input">
+                    <option value="spike">Spike</option>
+                    <option value="ignition">Ignition</option>
+                    <option value="powerline">Powerline</option>
+                    <option value="broadband">Broadband</option>
+                  </select>
+                </label>
                 <label class="wfm-control" id="sdr-dig-sideband-wrap" style="display:none;">
                   <span class="wfm-control-label" title="Sideband used to demodulate DIG. Auto = USB &ge; 10 MHz, LSB below.">DIG sideband</span>
                   <select id="sdr-dig-sideband" class="status-input">