feat(ui): add MicroSteps component with decompose button, step checklist, and Just Start timer

src/lib/components/MicroSteps.svelte

@@ -0,0 +1,111 @@
+<script>
+  import { invoke } from '@tauri-apps/api/core';
+  import { ListTree, Check, Timer, Loader2 } from 'lucide-svelte';
+
+  let { parentTaskId, reduceMotion = false } = $props();
+
+  let subtasks = $state([]);
+  let loading = $state(false);
+  let error = $state('');
+  let decomposing = $state(false);
+
+  async function loadSubtasks() {
+    loading = true;
+    error = '';
+    try {
+      subtasks = await invoke('list_subtasks_cmd', { parentTaskId });
+    } catch (e) {
+      error = String(e);
+    } finally {
+      loading = false;
+    }
+  }
+
+  async function decompose() {
+    decomposing = true;
+    error = '';
+    try {
+      subtasks = await invoke('decompose_and_store', { parentTaskId });
+    } catch (e) {
+      error = String(e);
+    } finally {
+      decomposing = false;
+    }
+  }
+
+  async function checkStep(subtaskId) {
+    try {
+      await invoke('complete_subtask_cmd', { subtaskId });
+      const idx = subtasks.findIndex(s => s.id === subtaskId);
+      if (idx >= 0) subtasks[idx] = { ...subtasks[idx], done: true };
+    } catch (_) {}
+  }
+
+  function startTimer(subtaskId) {
+    window.dispatchEvent(new CustomEvent('kon:start-timer', {
+      detail: { taskId: subtaskId, seconds: 120 }
+    }));
+  }
+
+  $effect(() => {
+    if (parentTaskId) loadSubtasks();
+  });
+</script>
+
+<div class="pl-6 mt-1 flex flex-col gap-1">
+  {#if loading}
+    <div class="flex items-center gap-2 text-[12px] text-text-tertiary py-1">
+      <Loader2 size={12} class="animate-spin" aria-hidden="true" />
+      Loading steps…
+    </div>
+  {:else if subtasks.length === 0 && !error}
+    <button
+      class="flex items-center gap-1.5 text-[12px] text-text-tertiary hover:text-accent py-1 disabled:opacity-50"
+      onclick={decompose}
+      disabled={decomposing}
+      aria-label="Break down this task into micro-steps"
+    >
+      {#if decomposing}
+        <Loader2 size={12} class="animate-spin" aria-hidden="true" />
+        Breaking down…
+      {:else}
+        <ListTree size={12} aria-hidden="true" />
+        Break down
+      {/if}
+    </button>
+  {:else if error}
+    <p class="text-[11px] text-text-tertiary py-1">{error}</p>
+  {:else}
+    {#each subtasks as step (step.id)}
+      <div class="flex items-center gap-2 group py-0.5">
+        <button
+          class="w-3.5 h-3.5 rounded border flex items-center justify-center flex-shrink-0
+            {step.done
+              ? 'bg-success/20 border-success text-success'
+              : 'border-border-subtle hover:border-accent'}"
+          onclick={() => checkStep(step.id)}
+          disabled={step.done}
+          aria-label={step.done ? 'Step complete' : 'Mark step complete'}
+        >
+          {#if step.done}
+            <Check size={9} aria-hidden="true" />
+          {/if}
+        </button>
+        <span class="text-[12px] flex-1 min-w-0 {step.done ? 'line-through text-text-tertiary' : 'text-text-secondary'} truncate">
+          {step.text}
+        </span>
+        {#if !step.done}
+          <button
+            class="opacity-0 group-hover:opacity-100 flex items-center gap-1 text-[10px] text-text-tertiary hover:text-accent"
+            onclick={() => startTimer(step.id)}
+            aria-label="Start 2-minute timer for this step"
+            style={reduceMotion ? '' : 'transition: opacity var(--duration-ui)'}
+          >
+            <Timer size={10} aria-hidden="true" />
+            Just Start
+          </button>
+        {/if}
+      </div>
+    {/each}
+  {/if}
+</div>