fix(vegas): stop capping plugin width by default (#445)

* fix(vegas): stop capping plugin width by default

Vegas plugins read as "cut off early" or "starting in the middle". That
was the per-plugin width budget, not the scroll engine:
overflow_mode=rotate is designed to resume mid-content on each
appearance, so the symptom was the feature working as specified.

Measured over a 17-plugin fleet on a 512px panel, the cap was a bad
trade. Only four plugins were ever wide enough to hit the 3.0 default --
leaderboard 11,518px, news 10,021px, odds-ticker 4,643px, hockey
1,508px. Weather is 650px and flights 512px; the cap never touched them
or the other eleven. So it bought nothing on thirteen plugins while
costing two visible faults on four: content entering mid-item (a news
ticker started at column 6027 of its own strip), and a final rotation
window of whatever happened to be left -- 348px of an 1,840px stocks
ticker, seven seconds of panel time.

Default max_plugin_width_ratio to 0 (uncapped), so every plugin
contributes all of its content and is always entered at its beginning.
The cap remains available, and vegas_max_width_screens still caps an
individual plugin -- which is where the knob belongs, since a genuinely
long ticker is a property of that plugin rather than of the fleet.

Verified on a live 512px device: 327 budget crops in the preceding six
hours, none after.

Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01Udr6MfaFLUPhX5Fgo67Jf5

* test(vegas): cover the width cap still working when asked for

Defaulting the cap off must not quietly remove it. Asserts that an
explicit ratio is honoured and validates, alongside the existing check
that omitting it means uncapped.

Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01Udr6MfaFLUPhX5Fgo67Jf5

---------

Co-authored-by: Claude Opus 5 (1M context) <noreply@anthropic.com>

web_interface/templates/v3/partials/display.html

@@ -556,11 +556,11 @@
                         </div>
 
                         <div class="form-group" id="setting-display-vegas_max_plugin_width_ratio" data-setting-key="display.vegas_scroll.max_plugin_width_ratio">
-                            <label for="vegas_max_plugin_width_ratio" class="block text-sm font-medium text-gray-700">Max Plugin Width (screens){{ ui.help_tip('Caps how much of one cycle a single plugin may occupy, measured in screen widths (0–20).\nDefault: 3. A long ticker such as a news feed or leaderboard is trimmed to this and the remainder shown on later cycles, so one plugin cannot hold the display for minutes. Set 0 for no limit.', 'Max Plugin Width') }}</label>
+                            <label for="vegas_max_plugin_width_ratio" class="block text-sm font-medium text-gray-700">Max Plugin Width (screens){{ ui.help_tip('Caps how much of one cycle a single plugin may occupy, measured in screen widths (0–20).\nDefault: 0 (no limit) — every plugin shows all of its content and always starts at the beginning.\nSet a limit to stop one long ticker holding the display for minutes: it is cut to this width and the remainder shown on later cycles. The trade-off is that such a plugin then resumes mid-content on each appearance instead of starting fresh.', 'Max Plugin Width') }}</label>
                             <input type="number"
                                    id="vegas_max_plugin_width_ratio"
                                    name="vegas_max_plugin_width_ratio"
-                                   value="{{ main_config.display.get('vegas_scroll', {}).get('max_plugin_width_ratio', 3.0) }}"
+                                   value="{{ main_config.display.get('vegas_scroll', {}).get('max_plugin_width_ratio', 0.0) }}"
                                    min="0"
                                    max="20"
                                    step="0.5"