feat(intentions): Phase 7 — if-then rules for task / time / triage triggers

Small if-then automation layer. Rules persist in SQLite; the runner
lives on the frontend and binds to the Phase 6 event bus so the rule
pipeline reuses the same delivery primitives (timer events, TTS,
Tasks navigation).

Storage:
- Migration v12 adds implementation_rules (id, enabled, trigger_kind,
  trigger_value, actions_json, last_fired_key, created_at,
  updated_at) with enabled+trigger_kind index for the runner's hot
  path.
- CRUD helpers: insert / list / get / set-enabled / mark-fired /
  delete, plus a round-trip test.

Commands (all main-window-guarded via ensure_main_window):
- list_implementation_rules
- create_implementation_rule — validates HH:MM, checks the target
  task exists at save time for surface-task actions, caps
  speak-line at 240 chars, pins v1 timers to 5 minutes.
- set_implementation_rule_enabled
- mark_implementation_rule_fired — main-thread idempotency shim so
  the runner can atomically claim a fire.
- delete_implementation_rule

Runner (implementationIntentions.svelte.ts):
- Subscribes to kon:task-completed and kon:morning-triage-finished
  (MorningTriageModal now emits on all three exit paths — empty,
  skipped, picked — so skip counts as finishing).
- 30 s poll for time-of-day rules, plus an immediate check on startup
  so a rule whose time has already passed today catches up once.
- Idempotency via last_fired_key composed as YYYY-MM-DD@HH:MM for
  time rules; new time rules whose HH:MM has already passed today
  are pre-seeded so they don't fire retroactively on save.
- Rules are paused when Nudges "Mute for now" is on — a hard mute
  stops all rule delivery in addition to OS notifications.
- Stale-task safety: if a surface-task action's target has been
  deleted, the runner opens Tasks and warns clearly rather than
  pretending to surface something that's gone.

Editor (ImplementationRulesEditor.svelte):
- Lives in Settings under a new "If-then rules" accordion section.
- `If` picker: time of day (with time input), a task completes,
  morning triage finishes.
- `Then` composer: optional surface (inbox / today / all tasks /
  specific task), optional 5-min timer, optional speak-aloud line.
- Saved rules list with enable toggle + delete.

Rules table integration for Phase 10b rename sweep: add
implementation_rules to the kon.db → corbie.db migration shim when
that phase lands.

Gates: fmt, clippy -D warnings, cargo test 265/0, svelte-check
0/0, npm build green. Pre-existing Vite chunk warning on sounds.ts
is unrelated to Phase 7.

src/lib/pages/SettingsPage.svelte

@@ -8,6 +8,7 @@
   import Toggle from "$lib/components/Toggle.svelte";
   import SegmentedButton from "$lib/components/SegmentedButton.svelte";
   import HotkeyRecorder from "$lib/components/HotkeyRecorder.svelte";
+  import ImplementationRulesEditor from "$lib/components/ImplementationRulesEditor.svelte";
   import ZonePicker from "$lib/components/ZonePicker.svelte";
   import AccessibilityControls from "$lib/components/AccessibilityControls.svelte";
   import { getPreferences, updatePreferences } from "$lib/stores/preferences.svelte.js";
@@ -1571,6 +1572,22 @@
         {/if}
       </div>
 
+      <!-- If-then rules (Phase 7 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 === 'rules' ? null : 'rules'}
+        >
+          <h3 class="font-display text-[18px] italic text-text">If-then rules</h3>
+          <span class="text-text-tertiary text-[16px] leading-none">{openSection === 'rules' ? '−' : '+'}</span>
+        </button>
+        {#if openSection === 'rules'}
+          <div class="px-5 pb-5 animate-fade-in">
+            <ImplementationRulesEditor />
+          </div>
+        {/if}
+      </div>
+
       <!-- Read aloud (Phase 4 roadmap) -->
       <div class="border-b border-border-subtle">
         <button