feat(web): re-land the goals wire domain as mutation-only ref acknowledgements

Six mutation RPCs (create/edit/pause/resume/complete/clear) move into
dsh-host-apiproxy (the PR's host/runtime carrier is gone): goalService()
resolves ctx.get('goals') with a loud absence error, mutateGoal() resolves
the session's agent (agentFor, the command.* implicit-resume precedent) and
acknowledges with the new CAS ref only. GoalError codes ride err.details.

goal.get and the wire GoalView/goalViewSchema are gone: the read side is the
'goal' session projection (whole values on the history tail page and
session/projection frames), so responses never feed client state — the rule
whose absence forced the original PR's write-revision fences.

packages/host/apiproxy/package.json

@@ -43,6 +43,7 @@
     "@deepseek-ai/dsh-agent": "workspace:^",
     "@deepseek-ai/dsh-brand": "workspace:^",
     "@deepseek-ai/dsh-commands": "workspace:^",
+    "@deepseek-ai/dsh-goal": "workspace:^",
     "@deepseek-ai/dsh-llm": "workspace:^",
     "@deepseek-ai/dsh-session": "workspace:^",
     "@deepseek-ai/dsh-session-persistence": "workspace:^",