fix: /approve and /deny outside REPL emit interactive_only error_kind (#828)

/approve, /yes, /deny, /no (and /y, /n) are valid REPL-only slash
commands. Outside the REPL they were falling through to
format_unknown_direct_slash_command -> error_kind:unknown_slash_command.

Fix: intercept them in the SlashCommand::Unknown arm and emit
interactive_only: prefix so classify_error_kind returns the correct kind.

One new test: approve_deny_outside_repl_emits_interactive_only (covers
/approve, /yes, /deny, /no)

572 tests pass, 1 pre-existing worker_boot failure unrelated.

ROADMAP.md

@@ -7888,3 +7888,9 @@ Original filing (2026-04-18): the session emitted `SessionStart hook (completed)
     **Required fix shape.** Introduce a typed `error_kind` for unrecognized slash commands (e.g. `unknown_slash_command` or `command_not_found`). Update the JSON emit in the `--resume` unknown-command handler to use the typed kind. Add regression coverage asserting the typed kind.
 
     **Acceptance.** `claw --resume latest --output-format json /bogus` exits rc=2, stdout `error_kind:"unknown_slash_command"` (or similar typed constant), stderr empty. [SCOPE: claw-code]
+
+828. **`/approve` and `/deny` outside REPL emit `unknown_slash_command` instead of `interactive_only`** — dogfooded 2026-05-29 16:05 on `main` `9d05573f`. `claw --output-format json /approve` exited rc=1 with `error_kind:"unknown_slash_command"` — these are valid REPL-only slash commands but are not `SlashCommand` enum variants, so they fell through to `format_unknown_direct_slash_command`. Machine consumers saw the wrong error class.
+
+    **Fix applied.** `SlashCommand::Unknown` arm now special-cases `approve | yes | y | deny | no | n` and emits `interactive_only:` prefix before falling through to `format_unknown_direct_slash_command`. Both `error_kind` and hint are correct.
+
+    **Acceptance.** `claw --output-format json /approve` exits rc=1, stdout `error_kind:"interactive_only"`, stderr empty. [SCOPE: claw-code]

rust/crates/rusty-claude-cli/src/main.rs

@@ -1739,7 +1739,20 @@ fn parse_direct_slash_cli_action(
                 }),
             }
         }
-        Ok(Some(SlashCommand::Unknown(name))) => Err(format_unknown_direct_slash_command(&name)),
+        Ok(Some(SlashCommand::Unknown(name))) => {
+            // #828: /approve and /deny are valid REPL-only slash commands that
+            // are not SlashCommand enum variants (they require an active tool
+            // call in the REPL to be meaningful). Emit interactive_only so
+            // machine consumers see the correct error_kind instead of
+            // unknown_slash_command.
+            if matches!(name.as_str(), "approve" | "yes" | "y" | "deny" | "no" | "n") {
+                Err(format!(
+                    "interactive_only: /{name} requires an active tool call in the REPL.\nStart `claw` and use /{name} to approve or deny a pending tool execution."
+                ))
+            } else {
+                Err(format_unknown_direct_slash_command(&name))
+            }
+        }
         Ok(Some(command)) => Err({
             let _ = command;
             format!(

rust/crates/rusty-claude-cli/tests/output_format_contract.rs

@@ -3993,3 +3993,25 @@ fn direct_unknown_slash_command_emits_typed_error_kind() {
         "direct unknown slash JSON must have empty stderr (#827)"
     );
 }
+
+// #828: /approve and /deny outside REPL must emit interactive_only, not unknown_slash_command
+#[test]
+fn approve_deny_outside_repl_emits_interactive_only() {
+    let root = unique_temp_dir("approve-deny-828");
+    std::fs::create_dir_all(&root).expect("create temp dir");
+    for cmd in &["/approve", "/yes", "/deny", "/no"] {
+        let output = run_claw(&root, &["--output-format", "json", cmd], &[]);
+        let stdout = String::from_utf8_lossy(&output.stdout);
+        let stderr = String::from_utf8_lossy(&output.stderr);
+        let j: serde_json::Value = serde_json::from_str(stdout.trim())
+            .unwrap_or_else(|_| panic!("{cmd} must emit JSON (#828), got: {stdout:?}"));
+        assert_eq!(
+            j["error_kind"], "interactive_only",
+            "{cmd} outside REPL must emit interactive_only (#828): {j}"
+        );
+        assert!(
+            stderr.is_empty(),
+            "{cmd} JSON must have empty stderr (#828): {stderr:?}"
+        );
+    }
+}