M0: compilable skeleton — Kigi 0.1.0 fork surgery

Hard fork of xai-org/grok-build (Apache-2.0) re-targeted as Kigi, an
unofficial Kimi Code CLI community build.

Rename & identity
- 72 xai-*/xai-grok-* crates -> kigi-* (explicit: xai-grok-pager-bin ->
  kigi-bin [binary `kigi`], xai-grok-pager -> kigi-tui; rest mechanical);
  ptyctl, ptyctl-cli, third_party/ unchanged; proto package
  xai.grok.tools.v1 -> kigi.tools.v1
- Config home ~/.kigi (KIGI_SHARE_DIR override), env prefix GROK_* ->
  KIGI_*, `kigi --version` carries the unofficial-community-build notice
- clap identity, help text, startup banner, prompt templates rebranded
  (templates re-encrypted)

Deletions (PRD removal list #5/#6/#7/#9/#10)
- voice input (xai-grok-voice) and all TUI wiring
- telemetry: Mixpanel client, external OTel stream, Sentry, OTLP layers,
  trace/GCS/S3 upload queues (kigi-file-utils halved), workspace upload
  module & dc_log, heap-profile uploader, auth-diagnostics uploader,
  session-analytics halves of feedback; local zero-egress observability
  preserved in new kigi-log crate (unified log, --debug firehose,
  subsystem file logs, opt-in instrumentation)
- announcements (crate, remote-settings fields, TUI surfaces)
- plugin marketplace (crate, sources/browse/CTA/extensions-modal tab);
  direct plugin install/uninstall/update via kigi-agent git_install kept
- relay/gateway/assets endpoints and features (agent relay, headless
  relay transport, gateway bridge, LeaderEnvUrls); leader IPC socket now
  ~/.kigi/leader.sock + KIGI_LEADER_SOCKET, no ws-url derivation
- functional types rehomed instead of deleted: PermissionMode ->
  kigi-config-types, McpInitStrategy -> kigi-mcp, PrCreationSource ->
  session signals, TerminalDiagnostics -> kigi-pager-render, agent_id ->
  shell util

Endpoints
- kigi-env rewritten: single production KigiEndpoints {coding_api_base_url
  https://api.kimi.com/coding/v1 (KIGI_CODE_BASE_URL), oauth_host
  https://auth.kimi.com (KIGI_OAUTH_HOST), update_base_url (GitHub
  Releases API), upgrade_page_url}; GrokBuildEnvironment enum deleted

Toolchain & workspace hygiene
- Rust 1.97.0 pinned; edition 2024; full cargo update; git2 hoisted to
  workspace at 0.21 (Option->Result API migration), quick-xml 0.41
- Root Cargo.toml hand-maintained (PRD §8.1): version 0.1.0 inherited by
  all members, members sorted, unused deps pruned
- cargo-deny advisories gate (deny.toml with documented transitive
  exceptions); CI workflow (check/clippy/fmt/deny/test, macOS+Linux)
- cross-crate test seams re-gated behind `test-support` cargo feature;
  insta snapshot baselines renamed to the kigi_tui prefix
- clippy --workspace --all-targets: zero warnings; fmt clean

Fixes surfaced by the port
- updater probe/installer divergence (bin/kigi vs bin/grok symlink set)
- idle model-metadata refresh dead under KIGI_CODE_BASE_URL override
  (new is_effective_coding_endpoint_url, loopback+override aware)
- macOS symlinked-TMPDIR fixture canonicalization (foreign_sessions,
  fast-worktree); RSS measurement tests serialized via serial_test

Docs & legal (Apache §4)
- NOTICE added (upstream attribution + change statement); THIRD-PARTY
  notices sustained; kigi-tools ported-code notices extended; README,
  CONTRIBUTING, SECURITY, AGENTS.md rewritten

Out of scope for M0 (tracked): Kimi auth/inference (M1), search/fetch,
command parity, config import (M2), Computer Hub excision & final
brand-token sweep (M2), distribution & self-update rewrite (M3).

crates/codegen/kigi-config/src/fs_atomic.rs

@@ -0,0 +1,43 @@
+//! Atomic file writes, shared by the managed-cache marker and the signature
+//! sidecar writers.
+
+use std::path::Path;
+
+/// Atomic temp + rename so a torn write can't leave a half-written file. The temp
+/// name is unique per writer (pid + counter) and `create_new`, so concurrent
+/// writers don't collide. `mode` (unix only) is applied at temp-file creation, so
+/// the final file never exists with looser permissions.
+pub(crate) fn write_atomically(
+    final_path: &Path,
+    contents: &str,
+    mode: Option<u32>,
+) -> std::io::Result<()> {
+    use std::io::Write as _;
+    use std::sync::atomic::{AtomicU64, Ordering};
+    static WRITE_NONCE: AtomicU64 = AtomicU64::new(0);
+
+    let dir = final_path.parent().unwrap_or_else(|| Path::new("."));
+    let name = final_path
+        .file_name()
+        .map(|n| n.to_string_lossy().into_owned())
+        .unwrap_or_else(|| "file".to_owned());
+    let nonce = WRITE_NONCE.fetch_add(1, Ordering::Relaxed);
+    let tmp = dir.join(format!("{name}.{}.{nonce}.tmp", std::process::id()));
+    let mut options = std::fs::OpenOptions::new();
+    options.write(true).create_new(true);
+    #[cfg(unix)]
+    if let Some(mode) = mode {
+        use std::os::unix::fs::OpenOptionsExt as _;
+        options.mode(mode);
+    }
+    #[cfg(not(unix))]
+    let _ = mode;
+    let result = options
+        .open(&tmp)
+        .and_then(|mut f| f.write_all(contents.as_bytes()))
+        .and_then(|()| std::fs::rename(&tmp, final_path));
+    if result.is_err() {
+        let _ = std::fs::remove_file(&tmp);
+    }
+    result
+}