fix vietnamese telex: qu-/gi- onset tone placement and dd+tone

transvi fixes:

1. qu-/gi- onset tone placement. The u after q, and the i after g when a
   vowel follows, are onset glides rather than the rime nucleus, so the
   tone must skip them: qua -> quá (was qúa), gia -> giá. The onset was
   previously passed straight through to the app, so transvi never saw it
   and toned the glide. Keep the onset in the preedit by adding qu-/gi-
   clusters to telex.map (mktelex.py onsets(), appended additively to the
   curated map), and add onsetglide() so transvi skips the glide. gi- with
   no following vowel keeps i as the nucleus (gì, gìn).

2. A tone key on a vowel-less preedit (e.g. "đ" from dd) now commits the
   preedit and lets the tone key pass through (eat=0), matching the engine
   commit-on-passthrough invariant, instead of eating it into the commit.

Verified against the running engine: qua/quan/quay/quê/quên/quyển,
gia/già/giàu/giữ/giúp/giống, gì/gìn, dd+s; unchanged mua->mùa, của, lúa;
all non-qu/gi words byte-identical to before.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

vi.c

@@ -89,12 +89,37 @@ applytone(Rune c, int tidx)
 	return c;
 }
 
+/*
+ * In qu- and gi- onsets the u/i is a glide that belongs to the onset,
+ * not the rime, so it must not bear the tone (qua -> quá, gia -> giá).
+ * The i of gi- is only a glide when another vowel follows; otherwise it
+ * is the nucleus itself (gì, gìn). Returns the rune index to skip, or -1.
+ */
+static int
+onsetglide(Str *m)
+{
+	Rune a, b;
+	int i;
+
+	if(m->n < 2)
+		return -1;
+	a = m->r[0];
+	b = removetone(m->r[1]);
+	if((a == 'q' || a == 'Q') && (b == 'u' || b == 'U'))
+		return 1;
+	if((a == 'g' || a == 'G') && (b == 'i' || b == 'I'))
+		for(i = 2; i < m->n; i++)
+			if(isvowel(removetone(m->r[i])))
+				return 1;
+	return -1;
+}
+
 Emit
 transvi(Im *im, Rune c)
 {
 	Emit e;
 	Str mapped, pre;
-	int i, tidx, vi, last, penult;
+	int i, tidx, vi, last, penult, glide;
 	Rune v, b1, b2;
 
 	if(!istone(c) && c != 'z')
@@ -115,9 +140,12 @@ transvi(Im *im, Rune c)
 	}
 	if(!mapget(im->l->map, &im->pre, &mapped))
 		mapped = im->pre;
+	glide = onsetglide(&mapped);
 	last = -1;
 	penult = -1;
 	for(i = 0; i < mapped.n; i++){
+		if(i == glide)
+			continue;
 		v = removetone(mapped.r[i]);
 		if(isvowel(v)){
 			penult = last;
@@ -140,9 +168,7 @@ transvi(Im *im, Rune c)
 		}
 	}
 	if(vi < 0){
-		e.eat = 1;
 		e.s = mapped;
-		sputr(&e.s, c);
 		return e;
 	}