fix(copy): replace em-dashes in user-facing strings with commas/periods

Per the project's no-dashes feedback rule (see CORBEL-Main memory
feedback_no_dashes.md), em-dashes in user-visible copy are the single
biggest "AI wrote this" surface tell. Forty-two occurrences across ten
files: ten in SettingsPage's group descriptions and option labels
(audio device picker, vocabulary help, prompt placeholders, model
descriptions), four in FirstRunPage's setup steps, three in
DictationPage / FilesPage / Energy chip tooltips, plus the privacy
bullets ("100% offline, no Python required, no cloud, no accounts,
no telemetry"), the rejection toast, MicroSteps thumb labels, and the
shutdown ritual prompts.

Replacement rule: subordinate-clause em-dashes followed by lowercase
become commas; sentence-break em-dashes followed by capitals become
full stops. Code comments left intact.

One non-em-dash regression caught while reviewing: TasksPage's energy
filter "no selection" placeholder showed "—" as a literal label; the
script changed it to a comma which read as a UI bug. Replaced with
"Any" instead.

src/lib/pages/DictationPage.svelte

@@ -1004,7 +1004,7 @@
       <Card classes="h-full flex flex-col">
         {#if transcriptionFailed && !transcript.trim() && !page.recording}
           <div class="flex-1 flex items-center justify-center">
-            <EmptyState icon={AlertTriangle} message="Something went wrong with that transcription. Your audio is saved — try again when you're ready." />
+            <EmptyState icon={AlertTriangle} message="Something went wrong with that transcription. Your audio is saved, try again when you're ready." />
           </div>
         {:else if !transcript.trim() && !page.recording && !transcribing}
           <div class="flex-1 flex items-center justify-center">