Let Fit fill the tile tab instead of stopping at 100 percent

Fit in the tile tab left the board small in the middle of the tab.
It used frameBoxes, which never zooms past 1 so that two graph nodes
do not blow up to fill the screen. The tile board is measured in image
pixels, though, and with 16 px tiles it is only about 345 x 186 px.

- frameBoxes takes a new cap parameter, default 1. The graph and the
  node board keep their behaviour.
- The tile tab passes its zoom limit of 6, so Fit fills the tab up
  to 600 percent.
- TileCanvas remembers whether the view is still the one Fit set.
  While it is, a change in the size of the tab or of the board fits
  again. After a pan or zoom by hand the view stays until Fit.

Found on the way: switching the image to another tile size (48 to
16 px) kept the old zoom, and the board shrank to a third. The refit
above covers that too.

Tests:
- ./check.sh: 161 files, 2370 tests, CHECK EXIT 0 (was 2369).
- New unit test in graph-framing: with a raised cap Fit fills the
  view up to the limit. The graph test for "not past 100 %" holds.
- e2e 39: ALL PASSED, 31 checks (was 29). Fit fills the tab at 48 px
  (zoom 0.41) and fits again after the switch to 16 px (zoom 1.24).
- Counter probes: a cap of 1 and no refit on a new board size each
  fail exactly the 16 px check (zoom 1 and zoom 0.41).
- e2e sum in the README is 1384, computed, not yet seen in CI.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

README.md

@@ -43,7 +43,7 @@ npm run build        # writes dist/ and regenerates index.html; the folder is wh
 The browser suite and the three example games need a machine with a GPU:
 
 ```bash
-node tools/seed-e2e.mjs && node tools/e2e.mjs      # the editor, 1382 checks (GM_STEPS=20 for one step)
+node tools/seed-e2e.mjs && node tools/e2e.mjs      # the editor, 1384 checks (GM_STEPS=20 for one step)
                                                    #   every tool signs in first – see the Accounts page
 node tools/seed-jumprun.mjs && node tools/smoke-jumprun.mjs
 node tools/seed-tetris.mjs && node tools/smoke-tetris.mjs