phraser: the reminder summary is cut in runes, and silence is an error (V-620)

Three defects in internal/phraser, all of the shape "reports done when
nothing happened".

The reminder summary was cut in bytes: `len(s) > 60` and `s[:57]`, in two
copies (Stub.PhraseReminder and LLMPhraser.PhraseReminder). On Russian a
letter is two bytes, so the cut fell at about 28 letters instead of 60 and
landed inside a letter about half the time. Sendable.Summary is what
voicesink hands to piper and what the telegram sink posts, so the half rune
was spoken and sent. One rune-counting helper now, shared by both. The test
that covered this was ASCII, which is what let the arithmetic stand.

The evidence branch of PhraseQuery and the bare-prose tail of PhraseChat
both returned ("", nil) when the server answered and the model wrote no
tokens. The knowledge branch has guarded that with errEmptyResponse since it
was written; these two did not. The daemon's callers check for the empty
string and paper over it, so the visible cost was the eval, which scored a
silent model as bad phrasing rather than as a failure, and a log line that
never appeared.

Stub.PhraseReminder set no Mood. Its sibling PhraseNudge sets "neutral" and
says in a comment why: the Stub is a production fallback and owes the output
contract a value. The zero value is not one of the five moods.

No prompt and no spoken wording changed, so the phrasing eval is unmoved.

internal/phraser/phraser.go

@@ -115,11 +115,32 @@ func (s *Stub) PhraseReminder(_ context.Context, d loop.ReminderDecision) (deliv
 	if text == "" {
 		text = "reminder"
 	}
-	summary := text
-	if len(summary) > 60 {
-		summary = summary[:57] + "..."
+	// Mood, for the same reason PhraseNudge sets it: the Stub is a production
+	// fallback, so it owes the output contract a value. This one was left at the
+	// zero value, which is not one of the five moods.
+	return delivery.PhrasedReminder{
+		Decision: d, Body: text, Summary: reminderSummary(text), Mood: "neutral",
+	}, nil
+}
+
+// summaryLimit — how much of a reminder goes to the away channels.
+const summaryLimit = 60
+
+// reminderSummary shortens a reminder body to the away-channel summary.
+//
+// Counted in runes. Both copies of this counted bytes — `len(s) > 60` and
+// `s[:57]` — and on a Russian reminder that is wrong twice. A Cyrillic letter is
+// two bytes, so the cut fell at about 28 letters rather than 60; and byte 57
+// lands inside a letter about half the time, so the summary ended in half a
+// rune. That is not cosmetic: Sendable.Summary is the text voicesink hands to
+// piper and the text the telegram sink posts, so the broken byte was spoken and
+// sent.
+func reminderSummary(body string) string {
+	r := []rune(body)
+	if len(r) <= summaryLimit {
+		return body
 	}
-	return delivery.PhrasedReminder{Decision: d, Body: text, Summary: summary}, nil
+	return string(r[:summaryLimit-3]) + "..."
 }
 
 // phraseNudge — the per-rule templates. each reads the context the predicate