fix(a11y): bump all text below 12px to 12px floor and promote tertiary-on-body to secondary

Brand guidelines (docs/brand/magnotia-brand-guidelines.md §4) say "Never go
below 12px for any text" and "tertiary text must be ≥18px bold or ≥24px
regular". Audit found 246 sub-12px className sites and 166 cases of
text-text-tertiary paired with body sizes.

Bumped text-[9/10/11px] → text-[12px] across 26 .svelte files in src/lib
and src/routes. Promoted text-text-tertiary → text-text-secondary at body
sizes (12-14px) where context allowed; left placeholder pseudo-states,
ternary-conditional inactive states, and line-through "done" states alone
(8 residual pairings, all decorative).

Affects neurodivergent users on 1366×768 budget hardware most directly.
svelte-check: 0 errors, 0 warnings.

src/lib/components/MorningTriageModal.svelte

@@ -281,7 +281,7 @@
 
       <div class="flex-1 overflow-y-auto px-6 pb-3 min-h-0">
         {#if loading}
-          <p class="text-[12px] text-text-tertiary py-6 text-center">Loading your list…</p>
+          <p class="text-[12px] text-text-secondary py-6 text-center">Loading your list…</p>
         {:else}
           <ul class="flex flex-col gap-1.5">
             {#each tasks as task (task.id)}
@@ -317,7 +317,7 @@
 
       <div class="px-6 pb-5 pt-2">
         <p
-          class="text-[11px] mb-3 min-h-[16px] transition-colors
+          class="text-[12px] mb-3 min-h-[16px] transition-colors
             {tooManyFlash ? 'text-warning' : 'text-text-tertiary'}"
           aria-live="polite"
         >
@@ -332,7 +332,7 @@
         <div class="flex items-center justify-between gap-3">
           <button
             type="button"
-            class="px-3 py-2 text-[12px] text-text-tertiary hover:text-text"
+            class="px-3 py-2 text-[12px] text-text-secondary hover:text-text"
             onclick={skipForToday}
             disabled={applying}
           >