chore: stage I1 -- repo cleanup, minimal README

Working plans (docs/development, docs/design redesign notes) removed; the
two developer guides moved to docs/developer/. README cut to devices,
flashing, links and building (Wio Tracker L2 added); its feature list and
doc tables moved to docs/solo_features/README.md. RELEASE.md describes the
Solo release flow. Upstream's GitHub Pages workflow (docs.meshcore.io)
dropped, CLAUDE.md untracked, Buy Me a Coffee back in FUNDING.yml.

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

examples/companion_radio/ui-core/DmUnreadTable.h

@@ -4,7 +4,7 @@
 // and always read back clamped to what the ring still holds for that contact --
 // the same self-healing shape as MessageHistory::chUnread() for channels.
 //
-// Header-only UI Core model (see docs/development/ui-core.md); no drawing, no
+// Header-only UI Core model (see docs/developer/ui-core.md); no drawing, no
 // screen state.
 
 class DmUnreadTable {

examples/companion_radio/ui-core/SettingsSchema.h

@@ -1,5 +1,5 @@
 #pragma once
-// Declarative settings (docs/development/ui-core.md, step 4): one table of
+// Declarative settings (docs/developer/ui-core.md, step 4): one table of
 // NodePrefs options with their labels, value lists and side effects, so every
 // frontend renders the same settings without its own per-item code. ui-lvgl
 // draws it as switches and dropdowns, one page per Page below; ui-new still has

examples/companion_radio/ui-core/UiCore.h

@@ -1,6 +1,6 @@
 #pragma once
 // UI Core: hardware-independent UI state and logic shared by every frontend
-// (ui-new today, ui-lvgl later). See docs/development/ui-core.md.
+// (ui-new today, ui-lvgl later). See docs/developer/ui-core.md.
 //
 // The Core is MyMesh's Listener: it files incoming/outgoing messages into the
 // history, keeps the unread counters, runs the engines, and tells the frontend

examples/companion_radio/ui-core/UiCoreHost.h

@@ -4,7 +4,7 @@
 // does, and reports to the frontend through UiEventQueue. This interface is the
 // remainder -- calls that must stay synchronous with mesh processing, or whose
 // logic still lives in the frontend until its extraction step
-// (docs/development/ui-core.md). None of these may draw or block.
+// (docs/developer/ui-core.md). None of these may draw or block.
 
 class UiCoreHost {
 public:

examples/companion_radio/ui-core/UiEvents.h

@@ -2,7 +2,7 @@
 // Core → frontend events. Engines never call into the frontend (no drawing, no
 // sound, no display power); they push a tagged event here and the frontend
 // drains the queue from its own loop() and reacts in its own way (ui-new:
-// alert overlay + buzzer; ui-lvgl: a dialog). See docs/development/ui-core.md.
+// alert overlay + buzzer; ui-lvgl: a dialog). See docs/developer/ui-core.md.
 //
 // Fixed-size ring, no heap. When full the oldest event is dropped -- events are
 // hints for the view; the authoritative state stays queryable on the engines.