feat(nudges): Phase 6 — Margot soft-touch nudges via frontend nudge bus

Frontend-owned nudge bus that consumes in-app signals Corbie already
produces, applies suppression, and fans out to OS notification + an
optional TTS read-aloud. OS-wide keyboard/window activity detection
stays deferred per the revised roadmap — the plan before rewrite
would have been brittle on Wayland, permission-heavy on macOS, and
low-quality everywhere.

Triggers (v1, all in-app signals):
- inactivity_with_active_timer — timer running, window blurred ≥ 90 s,
  at least 60 s into the timer.
- pending_morning_triage — ritual enabled, past 10:00 local, last
  shown ≠ today. Polls every 5 min while focused.
- micro_step_idle — micro-step decomposition created, no child step
  or parent task completed within 15 min.

Suppression:
- Respects nudgesEnabled + nudgesMuted.
- No nudge while the app has focus (document.hasFocus).
- Hard cap 3 per rolling hour.
- Permission requested via @tauri-apps/plugin-notification on first
  delivery; denial is silently respected.

Rust side:
- tauri-plugin-notification registered + ACL entries on the main-
  window capability only (secondary windows can't fire nudges).
- commands::nudges::deliver_nudge — thin wrapper, security-guarded
  via ensure_main_window, delegates to the plugin. No DB writes —
  the roadmap's nudges-audit table is deferred until a concrete need
  emerges.

Frontend glue:
- nudgeBus.svelte.ts — subscribes to window events, applies
  suppression, calls deliver_nudge (+ tts_speak when speakAloud is
  on).
- kon:task-completed now dispatched on complete_task_cmd success.
- kon:microstep-generated + kon:step-completed dispatched from
  MicroSteps so the idle trigger can clear itself on any engagement.
- kon:focus-timer-cancelled added to focusTimer so the bus can reset
  its inactivity state on cancel, not only on natural completion.
- nudgeBus started from +layout.svelte onMount, stopped on destroy.

Settings:
- New "Nudges" section with three toggles: Enable nudges, Mute for
  now (separate so a hard mute doesn't lose preferences),
  Speak nudges aloud (reuses Phase 4 TTS).
- All default OFF. No first-run prompt — nudges are a Settings-found
  feature rather than a walkthrough step.

Out of scope per the revised Phase 6 spec: OS-wide keyboard/window
hooks, biometric signals, custom trigger editor (Phase 7), notification
sound (platform variance too high for Layer-1 — revisit in Phase 9
polish with a bundled .wav).

Gates: fmt clean, clippy -D warnings clean, cargo test 262/0 (4
existing + 262 current), npm run check 0/0, npm run build green.

src/lib/pages/SettingsPage.svelte

@@ -1532,6 +1532,45 @@
         {/if}
       </div>
 
+      <!-- Nudges (Phase 6 roadmap) -->
+      <div class="border-b border-border-subtle">
+        <button
+          class="flex items-center justify-between w-full py-4 px-5 text-left"
+          onclick={() => openSection = openSection === 'nudges' ? null : 'nudges'}
+        >
+          <h3 class="font-display text-[18px] italic text-text">Nudges</h3>
+          <span class="text-text-tertiary text-[16px] leading-none">{openSection === 'nudges' ? '−' : '+'}</span>
+        </button>
+        {#if openSection === 'nudges'}
+          <div class="px-5 pb-5 animate-fade-in">
+            <p class="text-[11px] text-text-tertiary mb-4">
+              Gentle, anticipatory reminders. Capped at 3 per hour. Never fires while you're looking at Corbie.
+            </p>
+
+            <Toggle
+              bind:checked={settings.nudgesEnabled}
+              label="Enable nudges"
+              description="Soft-touch notifications when a timer has been ticking while you're away, when a morning triage is waiting, or when a micro-step decomposition has sat untouched for 15 minutes."
+            />
+
+            {#if settings.nudgesEnabled}
+              <div class="pl-1 py-1 animate-fade-in">
+                <Toggle
+                  bind:checked={settings.nudgesMuted}
+                  label="Mute for now"
+                  description="Stops delivery without forgetting your settings. Flip back off when you want the nudges back."
+                />
+                <Toggle
+                  bind:checked={settings.nudgesSpeakAloud}
+                  label="Speak nudges aloud"
+                  description="Also reads the nudge out through your Read-aloud voice. Useful if you keep the sound off but look up sometimes."
+                />
+              </div>
+            {/if}
+          </div>
+        {/if}
+      </div>
+
       <!-- Read aloud (Phase 4 roadmap) -->
       <div class="border-b border-border-subtle">
         <button