refactor(server): providers report option differences once, after create, resume and apply

Providers used to write their own reports into the agent's options while a session was being
created, resumed or updated, which needed a growing set of reconciliation, baseline and
suppression rules to stay in step with the daemon.

The contract is now transactional. A provider opens or updates with the options it is given and
emits nothing while doing so; if the result differs it says so once, afterwards, as
`options_changed`. Live apply hands the provider only the keys the patch sets and the daemon stores
them onto the agent's current options when the provider accepts, so the last write wins. A change
the provider makes on its own is stored and forwarded, not undone. Removing an option drops the key
and sends nothing live. Controls carry no state; `options` is the only option state.

A legacy `agent.create.before` hook's `featureValues` edits are applied as a patch over the
returned options, so its deletions and replacements hold. The unreleased `aliases` field on option
choices is gone; a pre-v0.10 Codex Fast preference is reported once as the model's tier id.

packages/protocol/src/agent-types.ts

@@ -158,11 +158,6 @@ export interface AgentOptionChoice {
   value: string;
   label: string;
   description?: string;
-  /**
-   * Other stored option values that select this choice. A saved value the provider has since
-   * renamed still reads back as this choice.
-   */
-  aliases?: string[];
 }
 
 interface AgentOptionControlBase {

packages/protocol/src/messages.ts

@@ -365,7 +365,6 @@ export const AgentOptionChoiceSchema = z.object({
   value: z.string(),
   label: z.string(),
   description: z.string().optional(),
-  aliases: z.array(z.string()).optional(),
 });
 
 export const AgentOptionToggleControlSchema = z.object({