Add v0.9.0 release notes

docs/release-notes/v0.9.0.md

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+## 🏔️ v0.9.0 — "Scouting the Next Ridge"
+
+Before committing a rope team to the next pitch, a smart sherpa sends a scout ahead — checking
+the route, testing the anchors, and setting up radios so base camp hears every call. `v0.9.0` is
+that kind of release: new gear for inspecting how your apps talk to the outside world, a rebuilt
+foundation that will carry the expedition onto new mountains, and a crash-reporting relay so we
+never lose sight of a climber on the trail.
+
+### 🆕 New Features
+
+- **Deep Link Testing & AASA Validator** — Device and Simulator tools tabs now let you launch
+  deep links and validate Apple App Site Association and Android `assetlinks.json` files right
+  from the app, with structured results, entry-by-entry breakdowns, and raw JSON for the sceptics
+  at base camp. (#126)
+- **Android SDK first-run setup** — The packages page no longer drops newcomers at a blank cliff
+  face. A proper setup card suggests the standard Android Studio install location, lets you
+  browse for a custom folder, surfaces OpenJDK readiness, and routes you to Doctor or Settings
+  if Java is still missing. (#148)
+
+### ✨ Improvements
+
+- **DevFlow v1 spec foundation** — A new `IAppInspectorClient` abstraction sits between Sherpa
+  and MauiDevFlow, with a native v1 client, a legacy adapter, and a factory that probes each
+  agent's protocol version at runtime. Legacy agents keep working unchanged today, and the trail
+  is now cut for non-MAUI frameworks (Flutter, React Native, Expo) to rope in later. (#152)
+
+### 🐛 Bug Fixes
+
+- **Copilot auth on signed macOS builds** — Signed and notarized macOS builds could wrongly
+  report the Copilot CLI as missing or logged out because GUI-launched apps don't inherit your
+  shell environment. Sherpa now resolves the CLI from bundled and common install locations,
+  hands the SDK a stable user-scoped environment and working directory, serializes connect
+  checks, and makes "Check Again" actually check again. (#151)
+- **Linux Settings & Doctor menu** — The GTK toolbar gains a Doctor button and a proper native
+  ➜ Blazor navigation channel, so Settings and Doctor on Linux actually take you where the sign
+  says. (#138)
+
+### 🔧 Infrastructure
+
+- **Sentry crash & performance reporting** — Every Sherpa flavor (Mac Catalyst, Windows,
+  standalone macOS/AppKit, Linux GTK) now phones home to Sentry when things go sideways. The DSN
+  is never hardcoded — it's injected at CI publish time via the `SentryDsn` MSBuild property and
+  skipped entirely when absent, so local and fork builds stay silent. Events are tagged with app
+  version and commit SHA so we can tie a crash to an exact stretch of trail. (#153)
+
+---
+
+*The ridge ahead is longer than the one behind, but now we have scouts out front, a working
+radio, and a rebuilt harness that will fit more than one kind of climber.* 📡