fix: project sleds need claude CLI + extensions.worktreeConfig

Two issues that surfaced when story 1 ran in the adopted huskies-server
sled:

1. Dockerfile.base: the base image had no nodejs / claude CLI, so every
   coder agent spawn in an adopted project sled failed with
   `Unable to spawn claude: No viable candidates found in PATH`.  Install
   nodejs + @anthropic-ai/claude-code in the base image so every sled
   built from it can spawn agents out of the box.

2. worktree/create.rs::install_pre_commit_hook: `git config --worktree`
   requires `extensions.worktreeConfig = true` to be set on the repo
   config; without it, every worktree creation logged a noisy
   `Pre-commit hook install failed` warning.  Enable the extension
   idempotently before the per-worktree hooks-path set so the hook
   install succeeds cleanly.

After this, rebuild huskies-project-base and recreate any adopted
project containers to pick up the CLI.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

docker/Dockerfile.base

@@ -27,6 +27,9 @@ RUN apt-get update && apt-get install -y --no-install-recommends \
         procps \
         openssh-server \
         sudo \
+        nodejs \
+        npm \
+    && npm install -g @anthropic-ai/claude-code \
     && rm -rf /var/lib/apt/lists/*
 
 # Copy the huskies binary and entrypoint from the main image.

server/src/worktree/create.rs

@@ -152,9 +152,17 @@ pub fn install_pre_commit_hook(wt_path: &Path) -> Result<(), String> {
     std::fs::set_permissions(&hook_path, std::fs::Permissions::from_mode(0o755))
         .map_err(|e| format!("chmod pre-commit hook: {e}"))?;
 
+    // `git config --worktree` requires `extensions.worktreeConfig = true` on
+    // the repository config; enable it idempotently before the per-worktree
+    // hooks-path set below.  Writing without `--worktree` targets the main
+    // GIT_DIR/config which all worktrees share, so a single call is enough.
+    let _ = std::process::Command::new("git")
+        .args(["config", "extensions.worktreeConfig", "true"])
+        .current_dir(wt_path)
+        .output();
+
     // Point git at the per-worktree hooks dir so only this worktree uses
     // these hooks (not the main repo or other worktrees).
-    // Requires extensions.worktreeConfig = true in the repository config.
     let output = std::process::Command::new("git")
         .args(["config", "--worktree", "core.hooksPath", ".git-hooks"])
         .current_dir(wt_path)