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/queue.rs

@@ -876,13 +876,9 @@ mod tests {
             kind: crate::app::agent::QueueEntryKind::Prompt,
         };
 
-        // Turn ends → should NOT drain "second" (user is editing it), only FetchBilling.
+        // Turn ends → should NOT drain "second" (user is editing it).
         let effects = dispatch(end_turn(), &mut app);
-        assert_eq!(effects.len(), 1);
-        assert!(matches!(
-            &effects[0],
-            Effect::FetchBilling { silent: true, .. }
-        ));
+        assert!(effects.is_empty(), "drain should be blocked: {effects:?}");
         assert!(app.agents[&id].session.state.is_idle());
         // "second" should still be in the queue.
         assert_eq!(app.agents[&id].session.queue_len(), 2);
@@ -908,14 +904,10 @@ mod tests {
             kind: crate::app::agent::QueueEntryKind::Prompt,
         };
 
-        // Turn ends → should drain "second" (front, not being edited) + FetchBilling.
+        // Turn ends → should drain "second" (front, not being edited).
         let effects = dispatch(end_turn(), &mut app);
-        assert_eq!(effects.len(), 2);
+        assert_eq!(effects.len(), 1);
         assert!(matches!(&effects[0], Effect::SendPrompt { text, .. } if text == "second"));
-        assert!(matches!(
-            &effects[1],
-            Effect::FetchBilling { silent: true, .. }
-        ));
         // "third" should still be in queue.
         assert_eq!(app.agents[&id].session.queue_len(), 1);
         assert_eq!(app.agents[&id].session.pending_prompts[0].text, "third");
@@ -1809,13 +1801,9 @@ mod tests {
             kind: crate::app::agent::QueueEntryKind::Prompt,
         };
 
-        // End turn for p2 → should NOT drain p3 (being edited), only FetchBilling.
+        // End turn for p2 → should NOT drain p3 (being edited).
         let effects = dispatch(end_turn(), &mut app);
-        assert_eq!(effects.len(), 1);
-        assert!(
-            matches!(&effects[0], Effect::FetchBilling { silent: true, .. }),
-            "drain should be blocked, only billing refresh"
-        );
+        assert!(effects.is_empty(), "drain should be blocked: {effects:?}");
         assert_eq!(app.agents[&id].session.queue_len(), 2); // p3, p4
 
         // Simulate user saving edited text.