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/src/index.ts

@@ -57,6 +57,7 @@ export class ApiProxyService extends Service implements ApiProxy {
   readonly workspace: ApiProxy['workspace']
   readonly host: ApiProxy['host']
   readonly commands: ApiProxy['commands']
+  readonly goals: ApiProxy['goals']
   readonly skills: ApiProxy['skills']
   readonly events: ApiProxy['events']
   readonly respond: ApiProxy['respond']
@@ -74,6 +75,7 @@ export class ApiProxyService extends Service implements ApiProxy {
     this.workspace = api.workspace
     this.host = api.host
     this.commands = api.commands
+    this.goals = api.goals
     this.skills = api.skills
     this.events = api.events
     // createApiProxy returns closures (no `this` capture); bind only satisfies