feat(mavweb): /ecosystem page consuming Nexus/Praxis/Hexis + shell fixes

Add a read-only /ecosystem page that consumes the sibling services'
JSON APIs (Nexus entities, Praxis attention, Hexis capabilities),
fetched concurrently with honest per-panel error states. Siblings stay
headless — mavweb is their human surface (arch §16). Wired via mavweb
-nexus/-praxis/-hexis flags; mavweb joins the ecosystem compose network.

Fix mobile horizontal overflow across all pages: .content is a flex
child with default min-width:auto, so it refused to shrink below the
tables' intrinsic width. min-width:0 lets wide tables pan inside .scroll
instead of dragging the page sideways. Verified via CDP geometry check
(scrollWidth === clientWidth at 430px).

Also includes in-progress Ethos UI redesign, ecosystem deploy compose,
and planning docs.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

PLANS.md

@@ -0,0 +1,25 @@
+# Maven mavweb — Ethos migration plan
+
+## Task
+Adopt Ethos design language (#36, prio:3).
+
+## Scope
+- Go + html/template + vanilla CSS/JS
+- Add tokens.css with :root --ethos-* variables
+- Replace literal colors/spacing/radii
+- Restructure dash.html / history.html / notifications.html / trace.html into shell
+- Tables: sort/filter/resize/hide/pin/pagination
+- Row click → inspector
+- Keyboard: Ctrl+K, Ctrl+/, Esc, Enter, Space, Alt+←, Alt+→
+- Status vocabulary
+- Density Compact default
+
+## Notes
+Largest rewrite due to stack mismatch. No SPA migration — keep server-rendered.
+
+## Status
+- [x] PLANS.md created
+- [ ] tokens.css
+- [ ] Shell restructure per page
+- [ ] Tables refactor
+- [ ] Keyboard shortcuts