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-pager-minimal/src/auth.rs

@@ -141,7 +141,7 @@ pub(super) fn render_auth(buf: &mut Buffer, area: Rect, theme: &Theme, hint: &Mi
                 area,
                 y,
                 bottom,
-                Line::from(Span::styled("Sign in to Grok", bold)),
+                Line::from(Span::styled("Sign in to Kimi", bold)),
             );
             y = put_line(buf, area, y, bottom, Line::default());
             match url {
@@ -242,12 +242,13 @@ mod tests {
 
     #[test]
     fn device_user_code_parses_verification_url() {
+        // The live Kimi device flow returns this exact URL shape.
         assert_eq!(
-            device_user_code("https://accounts.x.ai/oauth2/device?user_code=ABCD-EFGH"),
+            device_user_code("https://www.kimi.com/code/authorize_device?user_code=ABCD-EFGH"),
             Some("ABCD-EFGH")
         );
         assert_eq!(
-            device_user_code("https://accounts.x.ai/oauth2/device"),
+            device_user_code("https://www.kimi.com/code/authorize_device"),
             None
         );
         assert_eq!(device_user_code("https://x/device?other=1"), None);
@@ -261,14 +262,14 @@ mod tests {
         let st = AuthState::Authenticating {
             request_seq: 1,
             handle: None,
-            auth_url: Some("https://accounts.x.ai/device?user_code=ABCD-EFGH".into()),
+            auth_url: Some("https://www.kimi.com/code/authorize_device?user_code=ABCD-EFGH".into()),
             mode: AuthMode::Device,
         };
         match minimal_auth_hint(&st) {
             MinimalAuthHint::SigningIn { url, code } => {
                 assert_eq!(
                     url.as_deref(),
-                    Some("https://accounts.x.ai/device?user_code=ABCD-EFGH")
+                    Some("https://www.kimi.com/code/authorize_device?user_code=ABCD-EFGH")
                 );
                 assert_eq!(code.as_deref(), Some("ABCD-EFGH"));
             }
@@ -308,7 +309,7 @@ mod tests {
         let area = Rect::new(0, 0, 80, 12);
         let mut buf = Buffer::empty(area);
         let hint = MinimalAuthHint::SigningIn {
-            url: Some("https://accounts.x.ai/device?user_code=ABCD-EFGH".into()),
+            url: Some("https://www.kimi.com/code/authorize_device?user_code=ABCD-EFGH".into()),
             code: Some("ABCD-EFGH".into()),
         };
         render_auth(&mut buf, area, &theme, &hint);
@@ -320,8 +321,11 @@ mod tests {
                 }
             }
         }
-        assert!(text.contains("Sign in to Grok"), "header: {text:?}");
-        assert!(text.contains("accounts.x.ai/device"), "url: {text:?}");
+        assert!(text.contains("Sign in to Kimi"), "header: {text:?}");
+        assert!(
+            text.contains("www.kimi.com/code/authorize_device"),
+            "url: {text:?}"
+        );
         assert!(text.contains("ABCD-EFGH"), "device code: {text:?}");
         assert!(
             text.contains("Waiting for approval"),