chore(openspec): archive host-agent-dependency-supervisor

Implementation verified on macOS (task 6.4 confirmed spawn + adoption
behavior). Archives the change under
openspec/changes/archive/2026-07-14-host-agent-dependency-supervisor/ and
syncs the delta spec into a new main capability at
openspec/specs/host-agent-dependency-supervisor/spec.md (5 baseline
requirements covering opt-in default, adopt-don't-fight, spawn, bounded
backoff restart, and lifecycle tied to Host Agent). openspec validate
--strict passes on the synced spec.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

openspec/changes/archive/2026-07-14-host-agent-dependency-supervisor/tasks.md

@@ -42,6 +42,6 @@
 - [x] 6.3 `openspec validate --strict` for this change.
 
   Result: `Change 'host-agent-dependency-supervisor' is valid`.
-- [ ] 6.4 Manual verification on macOS: start Host Agent with supervisor enabled and no Appium/Runtime running, confirm both are spawned and device reaches `idle`; then start Host Agent again with an already-running Appium, confirm it's adopted (not duplicated) and logged as such.
+- [x] 6.4 Manual verification on macOS: start Host Agent with supervisor enabled and no Appium/Runtime running, confirm both are spawned and device reaches `idle`; then start Host Agent again with an already-running Appium, confirm it's adopted (not duplicated) and logged as such.
 
-  **Deferred.** This session ran on Windows where the Appium/WebDriverAgent real-device workflow doesn't apply. To be executed on a macOS host per `docs/MACOS_IPHONE_SETUP.md` §9 once available.
+  Verified by the user on a macOS host following `docs/MACOS_IPHONE_SETUP.md` §9.