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/agent_view/render.rs

@@ -329,7 +329,6 @@ impl AgentView {
         let thinking_label = self.scrollback.thinking_fold_label();
         let selected_is_user_prompt = selected_entry.is_some_and(|e| e.block.is_user_prompt());
         let selected_is_agent_message = selected_entry.is_some_and(|e| e.block.is_agent_message());
-        let selected_is_credit_limit = selected_entry.is_some_and(|e| e.block.is_credit_limit());
         let mut hints = agent::build_hints(
             self.active_pane,
             &self.prompt,
@@ -355,7 +354,6 @@ impl AgentView {
             !self.visible_queue_is_empty(),
             selected_is_user_prompt,
             selected_is_agent_message,
-            selected_is_credit_limit,
             crate::terminal::terminal_context().shift_enter_unavailable(),
             self.scrollback_search.as_ref(),
         );
@@ -1300,7 +1298,6 @@ impl AgentView {
         self.hit_bg_status.rect = areas.get("bg_tasks").copied();
         self.hit_goal_status.rect = areas.get("goal").copied();
         self.hit_context.rect = areas.get("context").copied();
-        self.hit_credits.rect = areas.get("credits").copied();
         self.hit_plan_button.rect = areas.get("plan").copied();
         self.hit_queue_badge.rect = areas.get("queue").copied();
         self.hit_badge.rect = areas.get("badge").copied();
@@ -2041,23 +2038,6 @@ impl AgentView {
         }
         let mode_flags: &[PromptFlag] = &mode_flags_vec;
         let multiline = self.multiline_mode;
-        let usage_visible = self
-            .prompt
-            .slash_controller
-            .registry()
-            .get("usage")
-            .is_some();
-        let warning = self.credit_balance.as_ref().and_then(|bal| {
-            crate::views::credit_bar::usage_warning_for_session(
-                bal,
-                self.auto_topup.as_ref(),
-                usage_visible,
-                self.chat_kind,
-            )
-        });
-        let usage_warning_text: Option<String> = warning.as_ref().map(|(t, _)| t.clone());
-        let usage_warning = usage_warning_text.as_deref();
-        let usage_warning_critical = warning.is_some_and(|(_, critical)| critical);
         let model_label = match self.session.models.reasoning_effort {
             Some(eff) => format!("{model_id} ({eff})"),
             None => model_id,
@@ -2067,8 +2047,6 @@ impl AgentView {
                 model_name: &model_label,
                 flags: mode_flags,
                 multiline,
-                usage_warning,
-                usage_warning_critical,
             },
             PromptMode::EditingQueued { id, .. } => {
                 let pos = self.session.queue_position(*id).map(|i| i + 1).unwrap_or(1);
@@ -2077,8 +2055,6 @@ impl AgentView {
                     model_name: &editing_label,
                     flags: mode_flags,
                     multiline,
-                    usage_warning,
-                    usage_warning_critical,
                 }
             }
         };
@@ -2087,8 +2063,6 @@ impl AgentView {
                 model_name: label,
                 flags: &[],
                 multiline: false,
-                usage_warning,
-                usage_warning_critical,
             }
         } else {
             info