Gemini: count the App's per-line tables in the page budget

Found in M3 while checking floors with the radio on: a windowed page left
1.5 to 3 KB less than the 40 KB steady floor (Q86), radio or not. The
budget counted TextBuffer's index (8 B/line) but not the App's tables,
which also grew by doubling. Now 16 B/line, and the App sizes them
exactly. The FAQ (1051 lines, windowed): 38.5 -> 39.6 KB after, radio
asleep; 37.1 -> 39.0 KB with the radio listening.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01EhqxQ49eCju4CzKYNjZzwT

src/services/gemini_service.h

@@ -64,6 +64,10 @@ class GeminiService {
     static constexpr int kMaxLinkedPages = 30;           // Q83
     static constexpr size_t kIndexEvery = 64;            // lines between lineIndex entries
     static constexpr size_t kMaxLineBytes = 8192;        // longer lines are cut
+    // What a page costs per line on top of its text: TextBuffer's index (8) and the App's tables
+    // (type, first row, links: about 8). Counting only the first left the steady floor 1.5 to 3 KB
+    // short on a windowed page (found in M3).
+    static constexpr size_t kBytesPerLine = 16;
     static constexpr const char* kBookmarks = "/gemini/bookmarks.gmi";
     static constexpr const char* kStartUrl = "about:start";