Bring every copied template file to sneak/prompts next at dd4027b9 (closes #67)

REPO_POLICIES.md is the sneak/prompts next copy at commit
dd4027b907ef99cdc3187c215cc4d610b7a11efc. .gitignore and .dockerignore
are that commit's copies plus keyfunc's own /keyfunc entry: both now
ignore id_ecdsa_sk and id_ed25519_sk, the private key files ssh-keygen
writes for hardware-backed keys, and .dockerignore keeps out a
.git/config at any depth. The other copied files already matched that
commit. The template Dockerfile, scripts, Makefile and workflow have not
changed since keyfunc adapted them, and the new policy text asks nothing
new of keyfunc's Dockerfile: its gate phases install nothing and its
last stage already runs script/bootstrap.

Model: opus-5-5

.gitignore

@@ -42,7 +42,9 @@ node_modules/
 [iI][dD]_[rR][sS][aA]
 [iI][dD]_[dD][sS][aA]
 [iI][dD]_[eE][cC][dD][sS][aA]
+[iI][dD]_[eE][cC][dD][sS][aA]_[sS][kK]
 [iI][dD]_[eE][dD]25519
+[iI][dD]_[eE][dD]25519_[sS][kK]
 
 # The binary `make build` writes.
 /keyfunc