refactor: extract magic strings, decompose long functions, standardize error display

CLAUDE.md

@@ -132,6 +132,7 @@ cargo run -p kild -- complete my-branch                # Complete kild (PR clean
 - `crates/kild-paths` - Centralized path construction for ~/.kild/ directory layout (KildPaths struct with typed methods for all paths including `tls_cert_path()` and `tls_key_path()` for daemon TLS certs, and `fleet_dir()`, `fleet_project_dir()`, `fleet_dropbox_dir()` for fleet dropbox paths). Single source of truth for KILD filesystem layout.
 - `crates/kild-config` - TOML configuration types, loading, validation, and keybindings for ~/.kild/config.toml. Depends only on kild-paths and kild-protocol. Single source of truth for all KildConfig/Config/Keybindings types. Extracted from kild-core to enable fast incremental compilation of config-only changes.
 - `crates/kild-protocol` - Shared IPC protocol types (ClientMessage, DaemonMessage, DaemonSessionStatus, SessionStatus, ErrorCode), domain newtypes (SessionId, BranchName, ProjectId), and serde-only domain enums (ForgeType). Also provides `IpcConnection` for JSONL-over-Unix-socket-or-TCP/TLS client used by both kild-core and kild-tmux-shim with connection health checking via `is_alive()` and TLS variant via `connect_tls()`, and `AsyncIpcClient<R, W>` — a generic async JSONL client over any `AsyncBufRead + AsyncWrite` pair used by kild-ui. Also provides `pool` module with `take(socket_path)` and `release(conn)` functions — shared thread-local `IpcConnection` pool used by both kild-core and kild-tmux-shim. All public enums are `#[non_exhaustive]` for forward compatibility. Newtypes defined via `newtype_string!` macro for compile-time type safety. Deps: serde, serde_json, futures (tempfile, smol for tests). No tokio, no kild-core. Single source of truth for daemon wire format and IPC client.
+- `crates/kild-git` - Git worktree naming, health, project queries, and CLI helpers. `naming.rs` is the single source of truth for `KILD_BRANCH_PREFIX`, `kild_branch_name()`, and `kild_worktree_admin_name()`. Consumed by kild-core, kild-ui, and kild-tmux-shim.
 - `crates/kild-core` - Core library with all business logic, no CLI dependencies
 - `crates/kild` - Thin CLI that consumes kild-core (clap for arg parsing, color.rs for Tallinn Night palette output)
 - `crates/kild-daemon` - Standalone daemon binary for PTY management (async tokio server, JSONL IPC protocol, portable-pty integration). CLI spawns this as subprocess. Wire types re-exported from kild-protocol. Optionally binds a TLS-wrapped TCP listener (`bind_tcp`) alongside the Unix socket for remote access; self-signed cert auto-generated at `~/.kild/certs/` on first start.
@@ -148,7 +149,7 @@ cargo run -p kild -- complete my-branch                # Complete kild (PR clean
 - `agents/` - Agent backend system (amp, claude, kiro, gemini, codex, opencode, resume.rs for session continuity)
 - `daemon/` - Daemon client for IPC communication with auto-start logic (discovers kild-daemon binary as sibling executable). Connection pooling delegates to `kild_protocol::pool`. `tofu.rs` implements SHA-256 TOFU fingerprint verification for remote TCP/TLS connections. `mod.rs` exposes `set_remote_override()` for `--remote` CLI flag to route connections via TCP/TLS without touching handler signatures.
 - `editor/` - Editor backend system (Zed, VS Code, Vim, generic fallback) with registry.rs for detection and resolution chain (CLI > config > $VISUAL > $EDITOR > OS default via duti/xdg-mime > PATH scan)
-- `git/` - Git worktree operations via git2
+- `git/` - Git worktree operations via git2 (overlaps, removals, CLI shelling). Naming utilities (`kild_branch_name`, `KILD_BRANCH_PREFIX`) live in the separate `kild-git` crate.
 - `forge/` - Forge backend system (GitHub, future: GitLab, Bitbucket, Gitea) for PR operations
 - `config/` - REMOVED (moved to kild-config crate). kild-core re-exports all types from kild-config.
 - `projects/` - Project management (types, validation, persistence, manager)

crates/kild-core/src/cleanup/handler.rs

@@ -1007,8 +1007,8 @@ mod tests {
 
         git::test_support::init_repo_with_commit(repo_dir.path()).unwrap();
 
-        let branch_name = format!("kild/{branch_suffix}");
-        let admin_name = format!("kild-{branch_suffix}");
+        let branch_name = git::naming::kild_branch_name(branch_suffix);
+        let admin_name = git::naming::kild_worktree_admin_name(branch_suffix);
         git::test_support::create_branch(repo_dir.path(), &branch_name).unwrap();
 
         let worktree_path = worktree_base.path().join(&admin_name);

crates/kild-core/src/git/overlaps.rs

@@ -283,7 +283,7 @@ mod tests {
             .current_dir(dir)
             .output()
             .unwrap();
-        let kild_branch = format!("kild/{}", branch);
+        let kild_branch = crate::git::naming::kild_branch_name(branch);
         Command::new("git")
             .args(["checkout", "-b", &kild_branch])
             .current_dir(dir)