pkgs/id: .ssh-host-key (SSH host private key) gitignored nowhere — CWD-relative serve artifact one git add -A from commit #443

Summary

id serve with SSH enabled creates .ssh-host-key — the SSH host private key — as a bare CWD-relative file, and it is gitignored nowhere. Every sibling server-key/data file is protected repo-wide (.iroh*, .identity.db/.redb, events.redb, groups.jsonl, .id-worlds/); this one was left out. It is the #420/#432/#439 hazard shape, but the payload is a secret key, not data.

Evidence (on main f3ab579f)

• pkgs/id/src/world_ssh.rs:31 — pub const SSH_HOST_KEY_FILE: &str = ".ssh-host-key"; ("File, beside the other server keys, that holds the SSH host key.")
• pkgs/id/src/world_ssh.rs load_or_create_host_key (~:86-97) — on first use it generates a fresh Ed25519 private key and persists it with crate::store::write_private_file(path, pem).
• pkgs/id/src/commands/serve.rs:1041-1043 — serve passes the bare constant (no directory join) when an SSH port is configured.
• pkgs/id/src/main.rs:82-87 — all data paths are CWD-relative by design; without --data-dir/--new the file lands in the caller's working directory (a repo checkout for anyone developing or dogfooding inside this repo, and any in-repo --data-dir is likewise uncovered for this name).
• Root .gitignore:117-123 protects the whole sibling family at any depth: .iroh* (:117 — covers .iroh-key, .iroh-key-client, .iroh-store, .iroh-serve.lock, .iroh-allowed), .id-worlds/ (:118), .identity.db (:119), .identity.redb (:120), events.redb/events.redb.tmp (:121-122), groups.jsonl (:123). .ssh-host-key has no entry in the root .gitignore or pkgs/id/.gitignore.

Reproduced with origin/main's own .gitignore files in a scratch repo: git check-ignore -v .ssh-host-key (at repo root, pkgs/id/, and sub/deep/) exits 1 — NOT IGNORED — and the files show as ?? in git status; the controls .identity.redb and events.redb match .gitignore:120/:121 as expected.

git ls-tree -r origin/main | grep ssh-host is empty — the file is not tracked yet, so no git rm --cached is needed; this is purely preventive, like #439.

Why it matters

host_key_fingerprint (world_ssh.rs) is the trust-on-first-use check SSH clients rely on. Committing this file — one git add -A after a single SSH-enabled serve run from a repo directory — publishes the host private key, letting anyone impersonate the host to every client that pinned its fingerprint. The file is mode-restricted on disk (write_private_file), but git does not care about that.

Acceptance criteria

• Root .gitignore gains an unanchored .ssh-host-key entry beside the other pkgs/id entries (:117-123), so it is ignored at any depth.
• git check-ignore -v matches .ssh-host-key at the repo root, in pkgs/id/, and in a nested directory; creating a dummy .ssh-host-key leaves git status clean.
• Audit in the fix PR: enumerate the *_FILE / *_PATH / FILE_NAME constants in pkgs/id/src (KEY_FILE, CLIENT_KEY_FILE, STORE_PATH, SERVE_LOCK, ALLOWED_NODES_FILE in access.rs, SSH_HOST_KEY_FILE, event-store events.redb, groups groups.jsonl, and the world files under .id-worlds/) and confirm each is covered after the change — this file should be the last gap.
• No tracked file becomes ignored (git ls-files -ci --exclude-standard gains no entries).

Single-repo: world_ssh.rs / .ssh-host-key exist only in this repo (grep-verified absent from developing-today/opencode, developing-today/openchamber, dezren39/nix).