fix(led): preserve strip corners and feather the complete light field

Keep real end and corner emitters, robust decimal joins and wall-circle
sweep events. Render one positive-winding compound visibility clip so
Chromium cannot cancel or cut away overlapping light regions.

Add independent pixel oracles for glow falloff and wall-following tubes.
Replace the lossy fan-count limit with explicit cached-path bounds while
retaining the original timing and warm-cycle heap-growth limits.

Issue: #788
User-Visible: yes

docs/testing-notes/mutation-browser-guards.md

@@ -14,11 +14,11 @@ to prove that the Node witness actually kills it.
 | --- | ---: | --- |
 | Performance threshold | 4 | The witness measures real browser wall-time or frame work; a pure assertion cannot prove the budget. |
 | Browser harness integrity | 4 | The mutation breaks page-error, round-trip or page-registration observation in the browser harness itself. |
-| Paint, cascade and layer composition | 32 | The invariant depends on computed CSS, SVG paint, clipping, stacking or pixels produced by Chromium. |
+| Paint, cascade and layer composition | 36 | The invariant depends on computed CSS, SVG paint, clipping, stacking or pixels produced by Chromium. |
 | Pointer geometry and trusted interaction | 47 | The invariant depends on hit testing, pointer capture, touch/keyboard dispatch or live DOM geometry. |
 | Responsive DOM layout | 38 | The invariant depends on measured element boxes, responsive breakpoints, native/HA dialog shells or focusable target size. |
 | Custom-element and HA browser lifecycle | 101 | The invariant crosses Lit/custom-element lifecycle, browser storage/events, lazy loading or a complete HA-card state transition. |
-| **Total** | **226 / 200** | Above the guideline `mutation-gate --check` warns rather than fails (#699); each guard above it is held by its own reason in this inventory and its `because`. |
+| **Total** | **230 / 200** | Above the guideline `mutation-gate --check` warns rather than fails (#699); each guard above it is held by its own reason in this inventory and its `because`. |
 
 ## Measured effect
 
@@ -93,6 +93,10 @@ The invariant depends on computed CSS, SVG paint, clipping, stacking or pixels p
 - `iso-theme-dark-wall-rule-returns`
 - `led-badge-dropped`
 - `led-core-coloured-under-glow`
+- `led-field-endpoint-dropped`
+- `led-field-disc-cancels-fan`
+- `led-field-compound-clip-children`
+- `led-field-circle-events-missing`
 - `led-icon-not-suppressed`
 - `led-source-stays-round-at-anchor`
 - `led-static-live-ignored`