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-fast-worktree/src/copy/cow.rs

@@ -0,0 +1,117 @@
+//! Copy-on-Write file cloning using the reflink-copy crate.
+//!
+//! Uses reflink (CoW) when supported by the filesystem, with automatic
+//! fallback to regular copy.
+
+use std::path::Path;
+
+use anyhow::Result;
+
+/// Clone a file using CoW if supported, falling back to regular copy.
+///
+/// On filesystems that support it (APFS on macOS, Btrfs/XFS on Linux),
+/// this creates a reflink which shares data blocks until modified.
+/// On other filesystems, it performs a regular copy.
+pub(crate) fn clone_file(src: &Path, dest: &Path) -> Result<()> {
+    reflink_copy::reflink_or_copy(src, dest)?;
+    // reflink (FICLONE) only clones data blocks, creating the dest with
+    // default umask permissions. Explicitly propagate the source mode so the
+    // executable bit etc. survive on reflink-capable filesystems.
+    let perms = std::fs::metadata(src)?.permissions();
+    std::fs::set_permissions(dest, perms)?;
+    Ok(())
+}
+
+/// Recreate `dst` as a symlink pointing at `target`, replacing any existing
+/// entry at `dst`.
+///
+/// `symlink()` refuses to overwrite an existing path, so we remove `dst` first
+/// (a missing `dst` is not an error).
+pub(crate) fn replace_symlink(target: &Path, dst: &Path) -> std::io::Result<()> {
+    let _ = std::fs::remove_file(dst);
+    symlink_to(target, dst)
+}
+
+#[cfg(unix)]
+fn symlink_to(target: &Path, dst: &Path) -> std::io::Result<()> {
+    std::os::unix::fs::symlink(target, dst)
+}
+
+#[cfg(windows)]
+fn symlink_to(target: &Path, dst: &Path) -> std::io::Result<()> {
+    std::os::windows::fs::symlink_file(target, dst)
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+    use tempfile::TempDir;
+
+    #[test]
+    fn test_clone_file_with_fallback() {
+        let temp = TempDir::new().unwrap();
+        let src = temp.path().join("source.txt");
+        let dest = temp.path().join("dest.txt");
+
+        std::fs::write(&src, "hello world").unwrap();
+
+        // Should work either via CoW or fallback
+        clone_file(&src, &dest).unwrap();
+
+        assert!(dest.exists());
+        assert_eq!(std::fs::read_to_string(&dest).unwrap(), "hello world");
+    }
+
+    #[test]
+    fn test_clone_file_binary() {
+        let temp = TempDir::new().unwrap();
+        let src = temp.path().join("source.bin");
+        let dest = temp.path().join("dest.bin");
+
+        let data: Vec<u8> = (0..=255).collect();
+        std::fs::write(&src, &data).unwrap();
+
+        clone_file(&src, &dest).unwrap();
+
+        assert_eq!(std::fs::read(&dest).unwrap(), data);
+    }
+
+    #[test]
+    fn test_clone_preserves_permissions() {
+        use std::os::unix::fs::PermissionsExt;
+
+        let temp = TempDir::new().unwrap();
+        let src = temp.path().join("script.sh");
+        let dest = temp.path().join("script_copy.sh");
+
+        std::fs::write(&src, "#!/bin/bash\necho hello").unwrap();
+
+        // Make executable
+        let mut perms = std::fs::metadata(&src).unwrap().permissions();
+        perms.set_mode(0o755);
+        std::fs::set_permissions(&src, perms).unwrap();
+
+        clone_file(&src, &dest).unwrap();
+
+        let dest_perms = std::fs::metadata(&dest).unwrap().permissions();
+        assert_eq!(dest_perms.mode() & 0o777, 0o755);
+    }
+
+    #[cfg(unix)]
+    #[test]
+    fn test_replace_symlink_overwrites_and_allows_dangling() {
+        let temp = TempDir::new().unwrap();
+        let dst = temp.path().join("link");
+
+        std::fs::write(&dst, "stale").unwrap();
+        // Target is intentionally dangling; it must still be created.
+        replace_symlink(Path::new("does-not-exist"), &dst).unwrap();
+
+        let meta = std::fs::symlink_metadata(&dst).unwrap();
+        assert!(meta.file_type().is_symlink(), "dst must be a symlink");
+        assert_eq!(
+            std::fs::read_link(&dst).unwrap(),
+            Path::new("does-not-exist")
+        );
+    }
+}