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>

CHANGELOG.md

@@ -19,6 +19,30 @@ accepts both, but the store flags the old spelling as deprecated
 
 ## Unreleased
 
+## 3.4.0
+
+Plugin-facing changes since 3.3.0 (tag `v3.3.1`) not covered further down:
+
+- `BasePlugin.get_update_interval()` (#555) — return seconds to override the
+  manifest's `update_interval` at runtime (e.g. poll fast only while a game is
+  live), or `None` to keep it. Clamped to at least 5 seconds; a raising or
+  non-numeric return is ignored. Called every scheduling tick, so keep it
+  cheap. Older cores never call it. See `docs/PLUGIN_API_REFERENCE.md`.
+- `src.common.scroll_config` (#523) — turns a plugin's scroll config into a
+  configured `ScrollHelper` in one place, replacing per-plugin resolution that
+  disagreed between tickers, and warns when a speed won't advance whole pixels
+  per panel refresh. Floor on 3.4.0 to import it.
+- **Skins are marked unsupported.** No current scoreboard plugin builds on
+  `src.base_classes`, so the skin hook (`SportsCore._render_game`) never runs.
+  The web UI no longer shows the Visual Skin dropdown, the store hides and
+  refuses `"type": "skin"` entries, and `GET /api/v3/skins` reports
+  `"supported": false`. Saved `skin` config values still load and save.
+  `src/skin_system/` is unchanged.
+- **Web preview size** now comes from `src/display_geometry.py`, the same
+  computation `DisplayManager` uses: double-sided setups preview one screen,
+  and a missing `chain_length` defaults to 2 everywhere (the Starlark magnify
+  default and the sync handshake used 1).
+
 **Per-element display customization, and the last mile of it into the web UI.**
 A user can set the font, size, colour, position, visibility and alignment of
 individual display elements per plugin -- and, where a plugin has display
@@ -109,6 +133,8 @@ Removed:
 
 ## 3.3.0
 
+Historical note: tag `v3.3.0` reports `__version__` "3.2.0" and tag `v3.3.1` reports "3.3.0", so a "3.3.0" floor is effectively `v3.3.1`, the first release shipping `src/common/sports_shared.py`.
+
 **The release the sports scoreboards floor on to delete their bundled copies.**
 3.2.0 shipped the unified sports library and made `ledmatrix_min_version`
 enforceable; this ships the last three shared modules and completes the store