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-test-support/src/env.rs

@@ -164,7 +164,7 @@ pub fn test_env_cmd_tokio(
         // prompt (the windows-x86_64 lifecycle "prompt timed out" failure).
         // Mirrors `leader.rs` and the pty-harness `env_for_pager`.
         .env("KIGI_SHARE_DIR", home.join(".kigi"))
-        .env("KIGI_CLI_CHAT_PROXY_BASE_URL", mock_url)
+        .env("KIGI_CODE_BASE_URL", mock_url)
         .env("KIGI_XAI_API_BASE_URL", mock_url)
         .env("XAI_API_KEY", "test-key-for-ci")
         .env("KIGI_TELEMETRY_ENABLED", "false")

crates/codegen/kigi-test-support/src/leader.rs

@@ -141,7 +141,7 @@ impl LeaderStdioClient {
             // leader subprocess inherits/forwards this env var, so every
             // (re-)elected leader binds the same sandboxed path.
             .env("KIGI_LEADER_SOCKET", home.join(".kigi").join("leader.sock"))
-            .env("KIGI_CLI_CHAT_PROXY_BASE_URL", server.url())
+            .env("KIGI_CODE_BASE_URL", server.url())
             .env("KIGI_XAI_API_BASE_URL", server.url())
             .env("XAI_API_KEY", "test-key-for-ci")
             .env("KIGI_TELEMETRY_ENABLED", "false")