Suggestions: stop re-nagging resolved edits + fix typographic anchoring

Two fixes for the "accept Petal's change, then it nags about the same
sentence moments later" report:

- replacePending now suppresses any freshly-generated suggestion whose
  original->replacement matches one the user already accepted or
  dismissed for that doc. The model has no memory between passes, so
  without this it re-proposes the identical edit on the next checkpoint.

- findRange anchored suggestions by exact string match, which missed
  whenever the model echoed an `original` with plain ASCII (straight
  quotes, --, ...) while the document held the Typography-converted
  glyphs (curly quotes, em-dash, single-char ellipsis). The miss meant
  no highlight AND a silent no-op on accept, which then fed the re-nag
  above. foldTypography canonicalizes those variants (with a source
  index map for length changes) so matching survives the mismatch.

Covered by a server-side regression test (accept+dismiss then re-check
returns nothing) and frontend unit tests for the fold and anchoring.

Claude-Session: https://claude.ai/code/session_016Yr6jELuRc7hyzYLccQKZd

internal/suggestions/handlers_test.go

@@ -127,6 +127,44 @@ func TestCheckpointFlow(t *testing.T) {
 	}
 }
 
+// TestResolvedSuggestionsNotReproposed proves a checkpoint won't re-nag a
+// sentence the user already accepted or dismissed: the model returns the same
+// raw batch on the next pass (it has no memory), but the resolved edits are
+// suppressed. This is the "accept it, then it nags again moments later" bug.
+func TestResolvedSuggestionsNotReproposed(t *testing.T) {
+	client := &stubClient{response: `{"suggestions":[
+		{"original":"I has","replacement":"I have","explanation":"subject-verb agreement","type":"grammar"},
+		{"original":"two apple","replacement":"two apples","explanation":"plural noun","type":"grammar"}
+	]}`}
+	srv, docID, h := newTestServer(t, client)
+	// Zero the checkpoint floor so the second pass runs instead of being throttled.
+	h.Limit = llm.NewRateLimiter(0)
+
+	rec := do(t, srv, http.MethodPost, "/docs/"+docID+"/check", "")
+	var got []db.Suggestion
+	_ = json.Unmarshal(rec.Body.Bytes(), &got)
+	if len(got) != 2 {
+		t.Fatalf("first pass: want 2, got %d", len(got))
+	}
+
+	// Accept one, dismiss the other.
+	do(t, srv, http.MethodPost, "/suggestions/"+got[0].ID+"/accept", "")
+	do(t, srv, http.MethodPost, "/suggestions/"+got[1].ID+"/dismiss", "")
+
+	// Second checkpoint returns the identical raw batch — both must be suppressed.
+	rec = do(t, srv, http.MethodPost, "/docs/"+docID+"/check", "")
+	if rec.Code != http.StatusOK {
+		t.Fatalf("second check: code=%d body=%s", rec.Code, rec.Body)
+	}
+	var again []db.Suggestion
+	if err := json.Unmarshal(rec.Body.Bytes(), &again); err != nil {
+		t.Fatalf("decode: %v", err)
+	}
+	if len(again) != 0 {
+		t.Fatalf("resolved suggestions should not be re-proposed, got %d: %+v", len(again), again)
+	}
+}
+
 // TestVoicePassCoexists proves the voice pass and the grammar checkpoint own
 // disjoint pending families: running one never wipes the other's flags, and
 // each endpoint returns the unified pending set.