fix(kon): rename ramble refs, fix export extensions, use shared constants in DictationPage

- Rename custom event from ramble:toggle-recording to kon:toggle-recording
- Change download filename prefix from ramble- to kon-
- Fix export extension mapping: csv and html formats now produce correct file extensions instead of falling through to .txt
- Add console.warn when PCM buffer exceeds 5-minute cap and gets truncated
- Replace magic numbers with shared constants (MAX_PCM_SAMPLES, MIN_CHUNK_SAMPLES, CHUNK_INTERVAL_MS, FEEDBACK_TIMEOUT_MS)
- Use shared pad() utility from time.js instead of inline reimplementation
- Remove unused saveTasks import
- Simplify redundant 3-branch append logic to 2 branches with clarifying comment
- Use $derived.by to avoid double transcript.trim() in wordCount

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

src/lib/pages/DictationPage.svelte

@@ -2,11 +2,13 @@
   import { onMount, onDestroy } from "svelte";
   import { invoke } from "@tauri-apps/api/core";
   import { listen } from "@tauri-apps/api/event";
-  import { page, settings, templates, addToHistory, addTask, tasks, saveTasks } from "$lib/stores/page.svelte.js";
+  import { page, settings, templates, addToHistory, addTask, tasks } from "$lib/stores/page.svelte.js";
   import Card from "$lib/components/Card.svelte";
   import ModelDownloader from "$lib/components/ModelDownloader.svelte";
   import { exportTranscript } from "$lib/utils/export.js";
   import { extractTasks } from "$lib/utils/taskExtractor.js";
+  import { pad } from "$lib/utils/time.js";
+  import { MAX_PCM_SAMPLES, MIN_CHUNK_SAMPLES, CHUNK_INTERVAL_MS, FEEDBACK_TIMEOUT_MS } from "$lib/utils/constants.js";
 
   let transcript = $state("");
   let segments = $state([]);
@@ -62,14 +64,14 @@
       handleResult(result);
     });
 
-    window.addEventListener("ramble:toggle-recording", hotkeyHandler);
+    window.addEventListener("kon:toggle-recording", hotkeyHandler);
 
     await checkModelState();
   });
 
   onDestroy(() => {
     if (unlisten) unlisten();
-    window.removeEventListener("ramble:toggle-recording", hotkeyHandler);
+    window.removeEventListener("kon:toggle-recording", hotkeyHandler);
     clearInterval(timerInterval);
     clearInterval(chunkTimer);
     if (page.recording) {
@@ -106,9 +108,9 @@
           });
         } else {
           // Append mode
-          if (transcript && result.chunk_id > 1) {
-            transcript += " " + text;
-          } else if (!transcript) {
+          // First chunk (id=1) starts the transcript; subsequent chunks append to it.
+          // When transcript is empty, assign directly; otherwise prepend a space separator.
+          if (!transcript) {
             transcript = text;
           } else {
             transcript += " " + text;
@@ -247,7 +249,7 @@
       page.status = "Recording...";
       page.statusColor = "#e87171";
       timerInterval = setInterval(updateTimer, 1000);
-      chunkTimer = setInterval(sendChunk, 3000);
+      chunkTimer = setInterval(sendChunk, CHUNK_INTERVAL_MS);
     } catch (err) {
       error = `Microphone access denied: ${err.message}`;
       page.status = "Error";
@@ -294,15 +296,16 @@
   }
 
   async function sendChunk() {
-    if (pcmBuffer.length < 8000) return;
+    if (pcmBuffer.length < MIN_CHUNK_SAMPLES) return;
     if (transcribing) return;
 
     chunkId++;
     const currentChunkId = chunkId;
     const samples = [...pcmBuffer];
     pcmBuffer = [];
-    if (samples.length > 4_800_000) {
-      samples.length = 4_800_000;
+    if (samples.length > MAX_PCM_SAMPLES) {
+      console.warn(`PCM buffer truncated from ${samples.length} to ${MAX_PCM_SAMPLES} samples (~5 min at 16 kHz)`);
+      samples.length = MAX_PCM_SAMPLES;
     }
     transcribing = true;
 
@@ -404,9 +407,7 @@
 
   function updateTimer() {
     const elapsed = Math.floor((Date.now() - startTime) / 1000);
-    const mins = Math.floor(elapsed / 60).toString().padStart(2, "0");
-    const secs = (elapsed % 60).toString().padStart(2, "0");
-    page.timerText = `${mins}:${secs}`;
+    page.timerText = `${pad(Math.floor(elapsed / 60))}:${pad(elapsed % 60)}`;
   }
 
   function copyAll() {
@@ -427,12 +428,13 @@
     if (!transcript) return;
     showExportMenu = false;
     const content = exportTranscript(transcript, segments, format);
-    const ext = format === "vtt" ? "vtt" : format === "srt" ? "srt" : format === "md" ? "md" : "txt";
+    const extMap = { vtt: "vtt", srt: "srt", md: "md", csv: "csv", html: "html" };
+    const ext = extMap[format] || "txt";
     const blob = new Blob([content], { type: "text/plain" });
     const url = URL.createObjectURL(blob);
     const a = document.createElement("a");
     a.href = url;
-    a.download = `ramble-${new Date().toISOString().slice(0, 10)}.${ext}`;
+    a.download = `kon-${new Date().toISOString().slice(0, 10)}.${ext}`;
     a.click();
     URL.revokeObjectURL(url);
   }
@@ -484,14 +486,15 @@
       language: settings.language,
     });
     saved = true;
-    setTimeout(() => { saved = false; }, 3000);
+    setTimeout(() => { saved = false; }, FEEDBACK_TIMEOUT_MS);
   }
 
   let taskCount = $derived(tasks.filter((t) => !t.done).length);
 
-  let wordCount = $derived(
-    transcript.trim() ? transcript.trim().split(/\s+/).length : 0
-  );
+  let wordCount = $derived.by(() => {
+    const trimmed = transcript.trim();
+    return trimmed ? trimmed.split(/\s+/).length : 0;
+  });
 </script>
 
 <div class="flex flex-col h-full animate-fade-in">