F3: Kimi inference pipeline + full grok cloud-surface excision

Sampler / inference (PRD F3):
- kimi_compat.rs: single adaptation point for the Kimi chat/completions
  dialect (thinking-field mapping, model_id stripping, empty-content
  tool-call message fix, stream_options.include_usage), with kimi-cli
  source citations
- Rate-limit handling reworked for Kimi/Moonshot semantics; UA kigi/{version}
- /models replaces the xAI models-v2 endpoint everywhere; idle model
  refresh carries X-Msh-* device headers only (X-XAI-Token-Auth and
  x-grok-client-mode/CLIENT_MODE_HEADER machinery deleted)

Cloud-surface excision (PRD §5, zero-egress):
- remote/ conversations lane, cli-chat-proxy-types crate, prod/ dir,
  share command, credit bar: deleted (single local session lane;
  paginate() replaces merge_and_paginate)
- Subscription/tier gate stack deleted end-to-end: AppView
  gate/tier/team/ZDR fields, app/subscription.rs watch loop,
  dispatch/billing.rs paywall + SuperGrok upsell, free-usage-exhausted
  chain, tier-restricted commands, GateInfo, RemoteSettings gate fields,
  SettingsUpdateNotification gate fields
- /privacy + coding-data-sharing setting deleted (backed by a dead xAI
  RPC; Kigi is zero-egress — nothing to share or retain remotely)

Auth UX correctness (user-reported):
- Device-flow fixtures now mirror the live Kimi payload shape
  (https://www.kimi.com/code/authorize_device?user_code=..., verified
  against auth.kimi.com); the fabricated auth.kimi.com/device?code=...
  URLs are gone
- open_browser_detached is a no-op under cfg(test): unit tests drove
  wiremock fixture URLs into the real browser (root cause of the
  "garbage mock link" ABCD-1234 tabs)
- Welcome/pager-minimal rebrand: Grok Build -> Kigi, grok.com ->
  kimi.com, "Sign in to Grok" -> "Sign in to Kimi"

crates/codegen/kigi-tui/src/app/dispatch/session/load.rs

@@ -162,8 +162,6 @@ fn dispatch_load_session_ungated(
             restore_degree: None,
             rate_limited: false,
             model_incompatible: false,
-            credit_limit_blocked: false,
-            free_usage_blocked: false,
             available_commands: app.bootstrap_acp_commands.clone(),
             available_commands_generation: 1,
             available_tools: None,
@@ -195,15 +193,8 @@ fn dispatch_load_session_ungated(
         agent_mut.session.start_command(AgentCommand::RestoreCode);
         agent_mut.turn_started_at = Some(std::time::Instant::now());
     }
-    agent_mut.apply_app_scoped_gates(
-        app.sharing_enabled,
-        app.usage_visible,
-        app.chat_mode,
-        app.screen_mode,
-        &app.tier_restricted_commands,
-    );
+    agent_mut.apply_app_scoped_gates(app.usage_visible, app.chat_mode, app.screen_mode, &[]);
     agent_mut.chat_kind = chat_kind || app.chat_mode;
-    agent_mut.apply_credit_balance(app.credit_balance.clone(), app.auto_topup.clone());
     agent_mut
         .prompt
         .slash_controller
@@ -808,8 +799,6 @@ pub(in crate::app::dispatch) fn dispatch_load_session_with_restore(
             restore_degree: None,
             rate_limited: false,
             model_incompatible: false,
-            credit_limit_blocked: false,
-            free_usage_blocked: false,
             available_commands: app.bootstrap_acp_commands.clone(),
             available_commands_generation: 1,
             available_tools: None,
@@ -836,15 +825,8 @@ pub(in crate::app::dispatch) fn dispatch_load_session_with_restore(
             .prompt
             .set_contextual_hints(app.contextual_hints.undo, app.contextual_hints.plan_mode);
         agent.set_session_recap_available(app.session_recap_available);
-        agent.apply_app_scoped_gates(
-            app.sharing_enabled,
-            app.usage_visible,
-            app.chat_mode,
-            app.screen_mode,
-            &app.tier_restricted_commands,
-        );
+        agent.apply_app_scoped_gates(app.usage_visible, app.chat_mode, app.screen_mode, &[]);
         agent.chat_kind = app.chat_mode;
-        agent.apply_credit_balance(app.credit_balance.clone(), app.auto_topup.clone());
         agent
             .prompt
             .slash_controller
@@ -958,10 +940,6 @@ pub(in crate::app::dispatch) fn handle_session_loaded(
             agent_id,
             session_id: hydrate_sid.clone(),
         });
-        effects.push(Effect::FetchBilling {
-            agent_id,
-            silent: true,
-        });
         if let Some((model_id, effort)) = deferred {
             agent.session.model_switch_pending = true;
             effects.push(Effect::SwitchModel {
@@ -1110,7 +1088,6 @@ pub(in crate::app::dispatch) fn handle_session_restored(
         supersede_open_reload_window(agent, agent_id, "SessionRestored");
         agent.bind_session_id(sid);
         agent.chat_kind = app.chat_mode;
-        agent.apply_credit_balance(app.credit_balance.clone(), app.auto_topup.clone());
         agent.scrollback.push_block(RenderBlock::system(format!(
             "Session restored. Loading {local_session_id}..."
         )));