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/acp_handler/session_notification.rs

@@ -342,8 +342,6 @@ pub(super) fn handle_session_notification(notif: &acp::ExtNotification, app: &mu
                 restore_degree: None,
                 rate_limited: false,
                 model_incompatible: false,
-                credit_limit_blocked: false,
-                free_usage_blocked: false,
                 bg_tasks: std::collections::BTreeMap::new(),
                 bg_tool_call_to_task: std::collections::HashMap::new(),
                 scheduled_tasks: std::collections::HashMap::new(),
@@ -363,7 +361,6 @@ pub(super) fn handle_session_notification(notif: &acp::ExtNotification, app: &mu
             child_view.set_input_mode(InputMode::Vim);
             child_view.is_subagent_view = true;
             child_view.active_pane = crate::views::agent::ActivePane::Scrollback;
-            child_view.set_sharing_enabled(agent.sharing_enabled);
             let usage_visible = agent
                 .prompt
                 .slash_controller
@@ -1087,18 +1084,6 @@ pub(super) fn handle_child_session_notification(
 /// Apply a compaction or retry event to a session's activity state and scrollback.
 ///
 /// Shared between the root agent and child (subagent) notification paths.
-/// Test-only shim so dispatch-level tests can replay real notification
-/// sequences (e.g. `RetryState::Retrying` → `Exhausted`) through the
-/// production handler — the Retrying arm clears the `in_flight_prompt`
-/// rewind stash, which a fixture setting fields directly would miss.
-#[cfg(test)]
-pub(crate) fn apply_session_event_for_test(
-    update: &XaiSessionUpdate,
-    session: &mut AgentSession,
-    scrollback: &mut crate::scrollback::state::ScrollbackState,
-) -> bool {
-    apply_session_event(update, session, scrollback, false)
-}
 pub(super) fn apply_session_event(
     update: &XaiSessionUpdate,
     session: &mut AgentSession,
@@ -1215,7 +1200,6 @@ pub(super) fn apply_retry_state(
     scrollback: &mut crate::scrollback::state::ScrollbackState,
     is_api_key_auth: bool,
 ) {
-    let mut is_credit_limit = false;
     let mut is_reauth = false;
     use kigi_shell::extensions::notification::RetryState;
     match retry {
@@ -1238,14 +1222,7 @@ pub(super) fn apply_retry_state(
             session.set_retry_activity(None);
             session.rate_limited = *rate_limited;
 
-            is_credit_limit = super::super::dispatch::is_credit_limit_error(None, reason);
-            let is_free_usage =
-                *rate_limited && super::super::dispatch::is_free_usage_exhausted_error(reason);
-            if is_credit_limit {
-                session.credit_limit_blocked = true;
-            } else if is_free_usage {
-                session.free_usage_blocked = true;
-            } else if !*rate_limited && is_reauthable_failure(None, reason) {
+            if !*rate_limited && is_reauthable_failure(None, reason) {
                 is_reauth = true;
                 scrollback.push_block(RenderBlock::session_event(SessionEvent::ReAuthRequired));
             } else {
@@ -1268,10 +1245,7 @@ pub(super) fn apply_retry_state(
             if error_type == "encrypted_content_mismatch" {
                 session.model_incompatible = true;
             }
-            is_credit_limit = super::super::dispatch::is_credit_limit_error(None, message);
-            if is_credit_limit {
-                session.credit_limit_blocked = true;
-            } else if is_reauthable_failure(Some(error_type.as_str()), message) {
+            if is_reauthable_failure(Some(error_type.as_str()), message) {
                 is_reauth = true;
                 scrollback.push_block(RenderBlock::session_event(SessionEvent::ReAuthRequired));
             } else if error_type == "context_length" {
@@ -1287,8 +1261,7 @@ pub(super) fn apply_retry_state(
             }
         }
     }
-    if is_credit_limit {
-    } else if !is_reauth {
+    if !is_reauth {
         session.in_flight_prompt = None;
     }
 }