feat(cli): keyed credentials — servers:, the token chain, login/logout (RFC-007 PR 2)

The operator config gains servers: (name -> url; never a token). A remote
command whose URL prefix-matches an operator server resolves its bearer
token through the keyed chain first — OMNIGRAPH_TOKEN_<NAME> env, then the
[<name>] section of ~/.omnigraph/credentials (created 0600 via temp+rename,
#139 finding 7; group/world-readable files refused loudly) — falling
through to the legacy chain unchanged. URL keying makes §D5 rule 3
structural: a token is only ever sent to the server it is keyed to.
Longest-prefix matching with a path-boundary check (http://h:8080 never
matches http://h:8080-evil). Inserting the keyed hop above the legacy chain
is safe by construction — no existing setup can have servers: defined.

omnigraph login <name> stores/rotates one section (token from --token or
one stdin line — the pipe flow keeps secrets out of shell history);
omnigraph logout removes it, idempotently; logging in before declaring the
server warns instead of failing (the gh model).

Coverage: URL-match/no-substring-trap, credentials round-trip preserving
sibling sections, 0600 write + over-permissive refusal, env-name mapping;
the legacy resolve test is now hermetic against a real ~/.omnigraph and
asserts byte-identical legacy behavior with no servers defined; one
spawned-binary e2e walks the whole lifecycle against an authed server:
refusal -> wrong-token login (stdin) -> rotate (--token) -> authorized read
-> env-beats-file -> non-matching-URL negative -> logout revokes.

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

crates/omnigraph-cli/src/main.rs

@@ -73,6 +73,29 @@ async fn main() -> Result<()> {
     };
     let http_client = build_http_client()?;
     match cli.command {
+        Command::Login { name, token, json } => {
+            let token = match token {
+                Some(token) => token,
+                None => {
+                    let mut line = String::new();
+                    std::io::stdin().read_line(&mut line)?;
+                    line
+                }
+            };
+            let Some(token) = normalize_bearer_token(Some(token)) else {
+                color_eyre::eyre::bail!(
+                    "no token provided: pass --token <TOKEN> or pipe it on stdin (echo $TOKEN | omnigraph login {name})"
+                );
+            };
+            let operator_config = crate::operator::load_operator_config()?;
+            let declared = operator_config.servers.contains_key(&name);
+            let path = crate::operator::write_credential(&name, &token)?;
+            finish_login(&name, &path, declared, json)?;
+        }
+        Command::Logout { name, json } => {
+            let path = crate::operator::remove_credential(&name)?;
+            finish_logout(&name, &path, json)?;
+        }
         Command::Version => {
             println!("omnigraph {}", env!("CARGO_PKG_VERSION"));
         }