fix(awareness): stop the subject echoing itself and cover the echo wiring

Remaining review follow-ups for the sonar pulses.

No self-echo: pulses are born 5 km out (startFraction of the radius),
but contacts nearer than that, the subject included, still lit on every
pulse birth. They now never echo. Just past the birth ring, an echo is
scaled with the front's own fade-in, so a bracket no longer flashes
before a visible front reaches it. The ring flash at the full radius is
unchanged.

Older Safari: the reduced-motion listener falls back to the media
query's addListener / removeListener when addEventListener is missing,
as other modules here already do.

Echo wiring test: a detectionHost test now paints through the real
detection lane with an echo field set, and checks the echo stroke takes
the echo colour on the default style and each style's line colour under
CRT, NVG and FLIR. CURRENT-STATE notes the 5 km no-echo zone.

docs/CURRENT-STATE.md

@@ -4957,7 +4957,7 @@ silently demoting every later lookup for the session.
 - Enabled Data Layer controls report normalized feed health on the button (`LOADING`, `DEGRADED`, `STALE`, `FALLBACK`, or `UNAVAILABLE`) while the metadata line retains the source and reason. A partial CelesTrak group failure keeps the usable catalog and reports `DEGRADED`; a total outage keeps last-good catalog data visible but reports `UNAVAILABLE`.
 - On activation it focuses the nearest currently observed aircraft across the civilian and military feeds, with military winning an exact distance tie; if none are available, it focuses an observed AIS vessel. The aircraft search is deliberately uncapped and one refresh-tick retry handles initially empty feeds. This is an attention-priority navigation shortcut, not a high-risk, affiliation, or threat classification.
 - A selected aircraft, AIS vessel, or mapped installation gets a 250 km **context window** with nearby cohort counts, nearest examples, source labels, and stale/unavailable reasons. It emits `NEARBY` or `UNKNOWN`; no detection, engagement, affiliation, or sensor-activity conclusion is calculated.
-- The window's edge is drawn on the globe as a 250 km range ring: a 4 px polyline with a 2 px Context-blue core inside a 1 px dark halo on each side, 2.5 km above the ellipsoid (`AWARENESS_RANGE_RING_STYLE` in `src/layers/awareness/policy.js`). The halo keeps it legible over bright desert and snow, dark ocean and forest, and under the FLIR, NVG and CRT styles, where the earlier 1 px ellipse outline disappeared. It is a polyline because WebGL draws ellipse outlines at 1 px whatever width is asked for. Three dim sonar pulses (3 px with a 1 px dark outline, same colours, at most 60% opacity) grow slowly from the subject at constant speed, one every 3 s and each taking 9 s, and arrive at the ring at about a third of that. Behind each pulse a radial gradient in the same blue fades inward over 35% of the radius. One unpickable 250 km disc draws both the pulse lines and the gradient, its shader reading the pulse radii and opacities each frame, so a click or tap near a pulse still reaches the contact underneath; the disc is rebuilt only after the subject moves 500 m, and not at all while the pulses rest, and it is hidden while the camera is below its 2.5 km height, where it would sweep across the sky. While pulses run, the ring dims to 40% and flashes to full strength as each pulse reaches it, fading over 1.8 s. As a pulse front crosses a flight, military aircraft or AIS vessel, the detection overlay draws a second bracket around that contact's own bracket, in the pulse blue on the default detection style and in the style's own line colour under NVG, FLIR and CRT, which spreads outward as it fades over 1.4 s (`AWARENESS_RANGE_ECHO`, read through `src/awarenessEcho.js`; no layer's icon is restyled, and mapped installations have no detection bracket). Pulses run for 9 s (three ring flashes) after a selection or a camera move, fading in and out over 1.2 s, then rest: the ring stays on screen at full strength, the pulses, gradient and echoes are hidden, and nothing asks for frames, so a parked Contacts view is quiet again. A moving subject does not wake them, since a flying subject moves on every refresh; a camera that follows a tracked aircraft does keep them running, but that follow already renders every frame. While they run they never hold continuous rendering: each drawn frame arms one render request 80 ms later (the Cyber sonar cadence, `CYBER_SONAR_RENDER_INTERVAL_MS`), so they repaint at about 12.5 fps and never beat the detection lane's 80 ms gate. Under `prefers-reduced-motion`, or in a scene without primitives or preRender and postRender hooks, there are no pulses or echoes and the ring stays on screen; changing the preference mid-session rebuilds the ring. The ring follows a moving subject once it has moved 250 m.
+- The window's edge is drawn on the globe as a 250 km range ring: a 4 px polyline with a 2 px Context-blue core inside a 1 px dark halo on each side, 2.5 km above the ellipsoid (`AWARENESS_RANGE_RING_STYLE` in `src/layers/awareness/policy.js`). The halo keeps it legible over bright desert and snow, dark ocean and forest, and under the FLIR, NVG and CRT styles, where the earlier 1 px ellipse outline disappeared. It is a polyline because WebGL draws ellipse outlines at 1 px whatever width is asked for. Three dim sonar pulses (3 px with a 1 px dark outline, same colours, at most 60% opacity) grow slowly from the subject at constant speed, one every 3 s and each taking 9 s, and arrive at the ring at about a third of that. Behind each pulse a radial gradient in the same blue fades inward over 35% of the radius. One unpickable 250 km disc draws both the pulse lines and the gradient, its shader reading the pulse radii and opacities each frame, so a click or tap near a pulse still reaches the contact underneath; the disc is rebuilt only after the subject moves 500 m, and not at all while the pulses rest, and it is hidden while the camera is below its 2.5 km height, where it would sweep across the sky. While pulses run, the ring dims to 40% and flashes to full strength as each pulse reaches it, fading over 1.8 s. As a pulse front crosses a flight, military aircraft or AIS vessel, the detection overlay draws a second bracket around that contact's own bracket, in the pulse blue on the default detection style and in the style's own line colour under NVG, FLIR and CRT, which spreads outward as it fades over 1.4 s (`AWARENESS_RANGE_ECHO`, read through `src/awarenessEcho.js`; no layer's icon is restyled, and mapped installations have no detection bracket). Pulses are born 5 km out, so the subject itself and anything nearer never echo. Pulses run for 9 s (three ring flashes) after a selection or a camera move, fading in and out over 1.2 s, then rest: the ring stays on screen at full strength, the pulses, gradient and echoes are hidden, and nothing asks for frames, so a parked Contacts view is quiet again. A moving subject does not wake them, since a flying subject moves on every refresh; a camera that follows a tracked aircraft does keep them running, but that follow already renders every frame. While they run they never hold continuous rendering: each drawn frame arms one render request 80 ms later (the Cyber sonar cadence, `CYBER_SONAR_RENDER_INTERVAL_MS`), so they repaint at about 12.5 fps and never beat the detection lane's 80 ms gate. Under `prefers-reduced-motion`, or in a scene without primitives or preRender and postRender hooks, there are no pulses or echoes and the ring stays on screen; changing the preference mid-session rebuilds the ring. The ring follows a moving subject once it has moved 250 m.
 - For a selected live aircraft or vessel, the context window refreshes from the existing tracker/feed position every 750 ms, so nearest distances and cohort counts follow the subject without introducing a duplicate poll loop.
 - Aircraft cohort membership uses every locally loaded, selectable contact inside the 250 km window, including a plane hidden only by horizon culling or because its 3D model owns the visual. Counts and navigation therefore do not change with the current camera angle or billboard/model handoff.
 - Nearby examples in the context panel are focus controls: they use their owning layer's existing selection/tracking path, then frame that contact. Static-installation distances use ellipsoidal surface distance so the count matches the ground-projected context disk.