chore: prepare the 3.8.0 release (#709)

* chore(deprecation): remove the 35 APIs deprecated for 3.8.0

The usage scan (docs/DEPRECATIONS_3.8.md, regenerated 2026-10-01 and
committed here) finds no call or override of any of them in the 46
monorepo plugins or the 8 third-party plugins plugins.json lists; the
only core callers were other deprecated methods removed alongside.

- CacheManager: 13 methods, plus the private helpers only
  has_data_changed used (_has_*_changed, _is_market_open).
- DisplayManager: 7 methods, plus WEATHER_COLORS and the private
  _draw_sun/_cloud/_rain/_snow/_storm helpers only the icon methods used.
- FontManager: 14 methods, plus size_tokens, _save_overrides and
  _clear_plugin_font_cache. font_overrides and _load_overrides stay:
  resolve_font() still applies config/font_overrides.json.
  performance_stats stays: get_font() keeps it and tests read it.
- PluginManager.get_enabled_plugins.

test_deprecation.py pins only the two 3.9.0 markers now; the scanner
tests run against a stand-in core instead of the real markers. The
memory-tier tests read stats through log_memory_cache_stats() and the
component, and the test of the removed _clear_plugin_font_cache goes.
Docs drop the removed methods' reference entries; the Deprecated APIs
table becomes "Removed in 3.8.0". CHANGELOG gains a Removed section.

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

* chore(deprecation): drop the test harness's copies of the removed icon methods

VisualTestDisplayManager still drew weather icons that DisplayManager no
longer has, so a plugin's visual tests could pass on calls that raise
AttributeError on the real display. Its draw_sun/draw_cloud/draw_rain/
draw_snow/draw_weather_icon/draw_text_with_icons, WEATHER_COLORS and the
private helpers go, with the tests that exercised them. The CHANGELOG's
Deprecations entries no longer say nothing is removed.

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

* chore: prepare the 3.8.0 release

Bumps src.__version__ to 3.8.0 and turns Unreleased into ## 3.8.0, with a
summary and a New modules list (vegas_elements, testing.vegas, sports_vegas;
display_watchdog, plugin_catalog, plugin_runtime) for plugins flooring on
3.8.0. Adds the CHANGELOG line #701's second commit lacked (blocks laid out
off the render thread).

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

* chore: 3.8.0 also ships what landed on main since the prep

#703, #705, #706 and #693 merged after this branch was cut; their CHANGELOG
entries now sit under 3.8.0. The summary and New modules list name them
(sports consolidation stage 4's four modules, src/ipc, field_model), stage
4's section says to floor on 3.8.0, and src/common/README.md marks its four
modules 3.8.0 instead of Unreleased.

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

---------

Co-authored-by: Claude Opus 5.5 <noreply@anthropic.com>

CHANGELOG.md

@@ -17,7 +17,37 @@ release that ships it.
 accepts both, but the store flags the old spelling as deprecated
 (`store_manager.py`) and only the new one is in `schema/manifest_schema.json`.
 
-## Unreleased
+## 3.8.0
+
+Live Vegas elements: plugin content that keeps changing while it scrolls
+(scores on the scoreboards' cards, the flight map's gliding aircraft, the
+weather radar's loop), with live games kept in the ticker by default. Also
+stable/beta update channels, the display control socket, the systemd
+display watchdog, optional web login, ES-module web UI pages, sports
+consolidation stage 4, and the removal of the 35 plugin APIs deprecated
+since 3.5.0 (see Removed).
+
+### New modules
+
+A plugin may import these via `src.*` once it floors on 3.8.0 (and should
+guard the import, since the loader's version check is advisory).
+
+- `src/plugin_system/vegas_elements.py` -- `VegasElement`, the unit a
+  plugin's `get_vegas_elements()` returns (also re-exported from
+  `base_plugin`). See "Live Vegas elements" below.
+- `src/plugin_system/testing/vegas.py` -- the harness for those hooks:
+  `render_vegas_elements`, `check_vegas_elements`, `render_vegas_timeline`.
+- `src/common/sports_vegas.py` -- what a scoreboard needs for live cards:
+  `game_key`, `game_fingerprint`, `dedupe_games`, `VegasCardCache`,
+  `StickyOdds`, `finished_games`.
+- `src/common/sports_plugin_host.py`, `sports_live_scroll.py`,
+  `sports_display_rules.py` and `sports_font_path.py` -- sports
+  consolidation stage 4; see "New modules (sports consolidation stage 4)"
+  below.
+- `src/display_watchdog.py`, `src/plugin_system/plugin_catalog.py`,
+  `src/plugin_system/plugin_runtime.py`, `src/plugin_system/field_model.py`
+  and the `src/ipc/` package -- new core modules (described below) that
+  plugins do not normally import.
 
 ### Web UI: ES modules and one form model (stage 1)
 
@@ -509,6 +539,14 @@ read any of them:
   twice. Assigning `cached_image` still stores exactly what was assigned.
   New `ScrollHelper.has_strip()` says whether there is a strip without
   building its image; the frame path and Vegas use it.
+- The frame after a Vegas strip extension is no longer late on a Pi 4. The
+  render thread also laid out every plugin block of the new group (joining
+  its rows, measuring the separation between each pair) and pasted the
+  blocks into one image, about 37ms on hdpi against ~3.75ms of slack. The
+  thread that fetches the group now does that as each plugin arrives, and
+  the extension only writes the prepared pixels into the strip
+  (`ScrollHelper.append_content` takes RGB arrays): 3.2ms. In a 4 x 8 minute
+  A/B soak, extension frames went from 10 of 10 late to 3 of 10.
 
 ### Tooling
 
@@ -616,12 +654,11 @@ plugin that still calls one gets an `AttributeError`;
 
 ### New modules (sports consolidation stage 4)
 
-A plugin may import these via `src.*` once it floors on the release that
-ships them (the first release cut from this section). All four hold code the
+A plugin may import these via `src.*` once it floors on 3.8.0. All four hold code the
 scoreboard plugins carry as identical copies (checked at ledmatrix-plugins
 `56c4f15`), moved without behaviour change under the plugins' own names;
 each docstring lists what the host class must provide. Nothing in core uses
-them yet. The plugins delete their copies when they floor on that release.
+them yet. The plugins delete their copies when they floor on 3.8.0.
 
 - `src/common/sports_plugin_host.py` — `SportsPluginHostMixin`, ten helpers
   of the scoreboard plugin class (`manager.py`) identical in all nine: