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-codebase-graph/src/manager/cache.rs

@@ -0,0 +1,106 @@
+//! Index caching for fast loading.
+//!
+//! Uses a custom binary format with magic bytes "SGIX" for the new interned format.
+//! Automatically detects and skips legacy bincode format (returns error so caller can rebuild).
+
+use std::path::Path;
+
+use crate::scope_graph::ScopeGraphIndex;
+
+/// Default cache file name.
+pub const CACHE_FILE_NAME: &str = ".goto_index.bin";
+
+/// Error type for cache operations.
+#[derive(Debug)]
+pub enum CacheError {
+    /// IO error.
+    IoError(std::io::Error),
+    /// Serialization error.
+    SerializeError(String),
+    /// Deserialization error.
+    DeserializeError(String),
+    /// Legacy format detected (caller should rebuild).
+    LegacyFormat,
+}
+
+impl std::fmt::Display for CacheError {
+    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
+        match self {
+            CacheError::IoError(e) => write!(f, "IO error: {}", e),
+            CacheError::SerializeError(msg) => write!(f, "Serialization error: {}", msg),
+            CacheError::DeserializeError(msg) => write!(f, "Deserialization error: {}", msg),
+            CacheError::LegacyFormat => write!(f, "Legacy cache format detected"),
+        }
+    }
+}
+
+impl std::error::Error for CacheError {}
+
+impl From<std::io::Error> for CacheError {
+    fn from(e: std::io::Error) -> Self {
+        CacheError::IoError(e)
+    }
+}
+
+/// Result type for cache operations.
+pub type Result<T> = std::result::Result<T, CacheError>;
+
+/// Get the default cache path for a repository.
+pub fn get_cache_path(root_path: &Path) -> std::path::PathBuf {
+    root_path.join(CACHE_FILE_NAME)
+}
+
+/// Load an index from cache.
+///
+/// Uses the new binary format with magic bytes "SGIX".
+/// Returns `CacheError::LegacyFormat` if the file uses the old bincode format,
+/// signaling to the caller that a rebuild is needed.
+pub fn load_index(cache_path: &Path) -> Result<ScopeGraphIndex> {
+    if !cache_path.exists() {
+        return Err(CacheError::IoError(std::io::Error::new(
+            std::io::ErrorKind::NotFound,
+            "Cache file not found",
+        )));
+    }
+
+    // Use ScopeGraphIndex::load which handles format detection
+    match ScopeGraphIndex::load(cache_path) {
+        Ok(Some(index)) => Ok(index),
+        Ok(None) => {
+            // None means legacy format was detected
+            tracing::info!(
+                cache_path = %cache_path.display(),
+                "Legacy cache format detected, will rebuild"
+            );
+            Err(CacheError::LegacyFormat)
+        }
+        Err(e) => Err(CacheError::IoError(e)),
+    }
+}
+
+/// Save an index to cache using the new binary format.
+pub fn save_index(cache_path: &Path, index: &ScopeGraphIndex) -> Result<()> {
+    index.save(cache_path).map_err(CacheError::IoError)
+}
+
+/// Save an index to cache asynchronously (in a background thread).
+///
+/// Returns immediately and spawns a thread to do the actual saving.
+/// Useful for saving the index without blocking the main thread.
+pub fn save_index_async(cache_path: std::path::PathBuf, index: ScopeGraphIndex) {
+    std::thread::spawn(move || {
+        if let Err(e) = save_index(&cache_path, &index) {
+            tracing::warn!("Failed to save index cache: {}", e);
+        }
+    });
+}
+
+/// Check if a cache exists and return its metadata.
+pub fn cache_exists(cache_path: &Path) -> bool {
+    cache_path.exists()
+}
+
+/// Get cache file size in bytes.
+pub fn cache_size(cache_path: &Path) -> Option<u64> {
+    std::fs::metadata(cache_path).ok().map(|m| m.len())
+}