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-workspace/src/permission/types.rs

@@ -76,7 +76,12 @@ pub struct PermissionEvent {
 pub enum ClientType {
     /// Generic client - show simple permission options with full command text
     #[default]
-    #[serde(rename = "generic", alias = "grok-shell", alias = "grok_shell")]
+    #[serde(
+        rename = "generic",
+        alias = "grok-shell",
+        alias = "grok_shell",
+        alias = "kigi"
+    )]
     Generic,
     /// Grok TUI client - show fancy options with interactive bash term selection
     #[serde(rename = "grok-tui", alias = "grok_tui")]
@@ -106,15 +111,18 @@ pub enum ClientType {
     Desktop,
 }
 impl ClientType {
-    /// Product token for the `User-Agent` header (e.g. `grok-pager`).
+    /// Product token for the `User-Agent` header. The first-party clients
+    /// (the bundled TUI/pager and the headless runner) all report `kigi`, so
+    /// their User-Agent collapses to `kigi/{version}` (PRD F3); the remaining
+    /// labels identify external ACP clients.
     pub fn user_agent_label(&self) -> &'static str {
         match self {
-            Self::Generic => "grok-shell",
+            Self::Generic => "kigi",
             Self::GrokTUI => "grok-tui",
             Self::GrokWeb => "grok-web",
             Self::Nebula => "nebula",
             Self::Extension => "grok-code-extension",
-            Self::GrokPager => "grok-pager",
+            Self::GrokPager => "kigi",
             Self::Desktop => "grok-desktop",
         }
     }