Add a 200ms click debounce with extensive behavioral tests

Per request: clicks of the same button closer together than
capture.clickDebounceMs (default 200ms) now collapse into a single step, so
accidental fast/double clicks don't each become a step. It is a leading-edge
debounce measured from the last *accepted* click, so a run of fast clicks
can't push the next deliberate click out — two clicks spaced beyond the
window (e.g. the reported 400-500ms apart) always register.

Replaces the prior 8ms duplicate-delivery suppression (subsumed by the
window). Configurable; 0 captures every click.

Tests (the point of this change is that it can't silently regress):
- 13 behavioral unit tests in capture.test.js that drive real onOsClick
  calls with controlled timestamps and assert which clicks survive — the
  reported 400/450/500ms cases, sub-window collapse, the 200ms boundary,
  per-button independence, configurability, debounce=0, last-accepted (not
  last-dropped) reference, session reset, and a full onOsClick -> queue ->
  store integration check. No keyword/comment assertions.
- A fourth end-to-end self-test scenario (burst of 40ms clicks collapses to
  1; three 300ms-apart clicks each register => 4 total). The marker/drain
  scenarios set debounce to 0 so they keep stressing the frame pipeline.

147 unit tests + all repo checks pass.

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

app/main.js

@@ -104,6 +104,11 @@ function createWindow() {
     if (process.env.STEPFORGE_CLICK_SELFTEST) {
       setTimeout(async () => {
         try {
+          // The marker/drain scenarios inject clicks faster than the default
+          // debounce to stress the frame pipeline; turn the debounce off for
+          // them so every injected click is captured. A dedicated scenario
+          // at the end re-enables it and verifies the debounce itself.
+          settings.set('capture.clickDebounceMs', 0);
           const guide = store.createGuide({ title: 'click selftest' });
           capture.startSession(guide.guideId, { intervalSec: 0 });
           // Isolate the test from the user's real mouse: the session starts
@@ -222,6 +227,41 @@ function createWindow() {
           console.log('CLICK-SELFTEST arm: first click ->', armStepIds.length,
             'step(s)', armPreClick ? '(see margin in [capture] log above)' : 'FAIL — first click lost');
           capture.finishSession();
+
+          // Fourth scenario: the debounce itself, exercised end to end through
+          // onOsClick. A fast burst (40ms apart) must collapse to one step,
+          // and deliberate clicks (300ms apart) must each register.
+          settings.set('capture.clickDebounceMs', 200);
+          const dbGuide = store.createGuide({ title: 'debounce selftest' });
+          mainWindow.show();
+          await new Promise((res) => setTimeout(res, 200));
+          capture.startSession(dbGuide.guideId, { intervalSec: 0 });
+          capture.stopClickWatcher();
+          capture.clickCaptureAvailable = () => true;
+          capture.hiddenForSession = true;
+          capture.togglePause(false);
+          await capture.startClickFrameBackend();
+          await new Promise((res) => setTimeout(res, 1500));
+          const dbPoint = {
+            x: Math.round(bounds.x + bounds.width * 0.55),
+            y: Math.round(bounds.y + bounds.height * 0.55),
+          };
+          // 4 clicks 40ms apart — accidental fast clicking → expect 1 step.
+          for (let i = 0; i < 4; i++) {
+            capture.onOsClick(Date.now(), toPhysical(dbPoint), 'button-1');
+            await new Promise((res) => setTimeout(res, 40));
+          }
+          // 3 deliberate clicks 300ms apart → expect 3 more steps.
+          for (let i = 0; i < 3; i++) {
+            await new Promise((res) => setTimeout(res, 300));
+            capture.onOsClick(Date.now(), toPhysical(dbPoint), 'button-1');
+          }
+          await capture.clickQueue;
+          await new Promise((res) => setTimeout(res, 800));
+          const dbSteps = store.getGuide(dbGuide.guideId).stepsOrder.length;
+          console.log('CLICK-SELFTEST debounce:', dbSteps, 'of 4 expected',
+            dbSteps === 4 ? 'OK — burst collapsed to 1, three deliberate clicks kept' : 'FAIL');
+          capture.finishSession();
         } catch (err) {
           console.log('CLICK-SELFTEST ERROR', err.message);
         } finally {