fix(display): pin one text layout engine, and give the 5x7 BDF face a size (#539)

* fix(display): pin one text layout engine, and give the 5x7 face a size

Two ways a font could render differently on two machines running the same
code, both found while diagnosing four plugins whose golden images passed on
the machine that generated them and failed everywhere else.

**Layout engine.** `ImageFont.truetype` picks its engine at load time: Raqm
where the host Pillow was built with libraqm, Basic otherwise. The two round
fractional glyph advances differently. `PressStart2P-Regular.ttf` at 8px has
whole-pixel advances, so they agree — which is why most of the fleet matched
everywhere and hid this. `4x6-font.ttf` at 6px does not: glyph positions drift
cumulatively along a run, and the four plugins that draw body text in it
(geochron, of-the-day, christmas-countdown, ledmatrix-weather's almanac) are
exactly the four whose goldens travelled badly.

Every core font load now goes through `src/common/font_layout.load_truetype`,
which pins the Basic engine, so a render depends on the font file and the size
and nothing else. Basic gives up complex-script shaping and kerning pairs;
neither applies to bitmap-grid faces on an LED panel. Output is unchanged on a
host without libraqm.

**Zero font height.** `DisplayManager` built the 5x7 BDF face with
`freetype.Face(path)` and never called `set_char_size`, so `face.size.height`
stayed 0 and `get_font_height()` returned 0 for it — callers stacking rows by
`prev_y + prev_height + gap` drew two lines on top of each other. The
start-up line `Calendar font size: 0 pixels` has been printing the symptom all
along. `font_manager._load_bdf_font` already called `set_char_size`, so
whether measurement worked depended on which path loaded the face.

`DisplayManager` now sets it too, and `get_font_height()` falls back to the
strike the file declares rather than returning a zero line height.

Fixes ChuckBuilds/ledmatrix-plugins#397
Refs ChuckBuilds/ledmatrix-plugins#371, #375, #378, #391

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>

* fix(display): give the startup banner a rung that fits a full address at 64px

CI caught what pinning the layout engine exposed rather than caused.
`_fitting_font` walks PressStart2P then 4x6 at 6px, and "255.255.255.255" --
the widest thing the startup banner ever shows -- measures 66px at 4x6/6px
against the 62 a 64x32 panel has to give. It used to squeak in only because
the measurement depended on which layout engine the host Pillow happened to
have; with the engine pinned it does not, so the rung the worst case actually
needs is now in the ladder instead of implied: 4x6 at 5px, which measures 51.

The fallback was wrong in the same place. When nothing in the ladder fit, it
returned `self.font` -- the *widest* option, and precisely how "Initializing"
came to run off the side of a 64px panel to begin with. It returns the
narrowest face that loaded now.

test/test_initializing_screen.py: 34 passed.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>

* fix(display): name the exceptions the BDF strike read can raise

Codacy flagged the try/except/pass. It was already narrow in intent -- a
malformed strike table on the measurement path must degrade to "size unknown"
rather than take the display down -- but a bare `except Exception: pass` says
neither of those things and hides a genuinely broken font behind a silent 8px
fallback. It now catches what reading `available_sizes` can actually raise and
logs which face failed.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>

* chore: drop logo PNGs the render harness downloaded into the worktree

These are fetched at runtime by the logo cache; they are not source, and they
rode in on a `git add -A` while I was running check_plugin.py against this
branch. Nothing in the change needs them.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>

---------

Co-authored-by: Claude Opus 5 <noreply@anthropic.com>

scripts/scroll_speeds.py

@@ -123,6 +123,8 @@ def demo(hardware, target, seconds):
     """Scroll text at the crisp speed nearest `target`."""
     from PIL import Image, ImageDraw, ImageFont
 
+    from src.common.font_layout import load_truetype
+
     hz = float(hardware.get("limit_refresh_rate_hz") or scroll_config.DEFAULT_REFRESH_HZ)
     choice = scroll_config.solve_crisp(target, hz)
     print("asked for {:.0f} px/s -> {}".format(target, choice.describe()))
@@ -137,7 +139,7 @@ def demo(hardware, target, seconds):
         ("/usr/share/fonts/truetype/dejavu/DejaVuSansMono-Bold.ttf", 26),
     ):
         try:
-            font = ImageFont.truetype(path, size)
+            font = load_truetype(path, size)
             break
         except OSError:
             continue