chore: mark skins unsupported, fix stale docs and preview size, prepare 3.4.0 (#580)

* chore: mark skins unsupported, fix stale docs and preview size, prepare 3.4.0

Skins: no current scoreboard plugin builds on src.base_classes, so the only
skin hook (SportsCore._render_game) never runs. The plugin schema endpoint no
longer injects the Visual Skin dropdown, the store hides and refuses
"type": "skin" registry entries, and GET /api/v3/skins reports
supported: false with a message. Stored skin config still loads and saves.
src/skin_system/ and its tests are unchanged apart from the support flag.

Docs: check_plugin.py/render_plugin.py examples use --plugin; document
BasePlugin.get_update_interval() and its interaction with the manifest
update_interval; CLAUDE.md drops the stale template line number and
recommends display_manager.width/height.

Preview size: new src/display_geometry.py holds the size computation and
defaults DisplayManager uses (double-sided applied, chain_length default 2).
The web preview, /display/current, Starlark magnify default, sync handshake
and two dev scripts use it.

Release: __version__ 3.4.0, CHANGELOG 3.4.0 section plus a 3.3.0 tag note.

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

* fix: address CodeRabbit review on #580

- Preview fallbacks (SSE stream and /display/current) use logical_size({})
  (128x32, the shared default) instead of a hard-coded 128x64.
- display_geometry treats a non-mapping display/hardware block as missing,
  so a malformed config.json falls back to defaults instead of raising
  AttributeError (which turned the Starlark render into an HTTP 500).
- Docs: the static update interval falls back manifest -> plugin config
  -> 60s, in both the API reference and the architecture spec.

Not taken: validating double_sided copies against chain_length/parallel.
An orientation Rotate: or U-mapper pixel mapper decides which axis panels
lie on, so the counts would reject working setups (the existing
vertical-split test is one).

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

* fix(display_geometry): a non-finite hardware size raises ValueError, not OverflowError

CodeRabbit flagged the Starlark magnify default in
_standalone_render_starlark_app for truthy non-mapping display values. That
case was already handled by a9e1bd0b (_display/_hardware treat a non-mapping
block as missing, covered by test_non_mapping_display_config_uses_the_defaults),
and the magnify it produces from the 128x32 defaults is the same as from 64x32.

Checking the same path found one input that still escaped: Python's JSON
parser accepts Infinity, and int(inf) raises OverflowError, which neither the
Starlark path (TypeError, ValueError) nor the preview stream in app.py caught,
so a hand-edited "rows": Infinity returned HTTP 500. physical_size now raises
ValueError for it, matching its documented contract, so every caller's
existing fallback applies. DisplayManager already caught Exception.

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

---------

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

src/common/sync_manager.py

@@ -32,6 +32,8 @@ from typing import Callable, Optional
 import numpy as np
 from PIL import Image
 
+from src.display_geometry import DEFAULT_CHAIN_LENGTH
+
 # Raw-frame wire format: 8-byte magic + 4-byte header + raw RGB pixels
 # Much faster than PNG: no encode/decode, negligible CPU, same UDP packet size
 _RAW_MAGIC = b'SYNC_RAW'
@@ -194,7 +196,7 @@ class DisplaySyncManager:
         local_cols = hw.get("cols", 64)
         peer_rows = int(msg.get("rows", 0))
         peer_cols = int(msg.get("cols", 0))
-        peer_chain = int(msg.get("chain", 1))
+        peer_chain = int(msg.get("chain", DEFAULT_CHAIN_LENGTH))
 
         compatible = peer_rows == local_rows and peer_cols == local_cols
 
@@ -589,7 +591,7 @@ class DisplaySyncManager:
             "t": "hello",
             "rows": hw.get("rows", 32),
             "cols": hw.get("cols", 64),
-            "chain": hw.get("chain_length", 1),
+            "chain": hw.get("chain_length", DEFAULT_CHAIN_LENGTH),
         }).encode("utf-8")
         heartbeat = json.dumps({"t": "hb"}).encode("utf-8")
         dest = ("<broadcast>", self.port)
@@ -660,7 +662,7 @@ class DisplaySyncManager:
             "port": self.port,
             "local_rows": hw.get("rows", 32),
             "local_cols": hw.get("cols", 64),
-            "local_chain": hw.get("chain_length", 1),
+            "local_chain": hw.get("chain_length", DEFAULT_CHAIN_LENGTH),
         }
 
         if self.role == SyncRole.STANDALONE: