fix: redact secrets nested inside metadata in servers/show

The redaction checked only top-level keys. That was sufficient while values
were strings — a secret could not hide beneath one — but #1910 lets a value be
an object, so `{ trace: { accessToken: "…" } }` printed in full: `trace` is not
sensitive, so the whole subtree went out with it. `servers/show` output is
meant to be safe to paste into an issue, so this is a regression this PR
introduced rather than a pre-existing gap.

`redactMetadataValue` walks the payload: a key matching `isSensitiveHeader`
replaces its entire value (so a sensitive key holding an object cannot leak
through its members either), anything else is descended into, and arrays are
mapped elementwise since objects inside them can carry sensitive keys.
Recursion is bounded — the payload came from `JSON.parse`, so it is a finite
tree with no cycles.

Tests cover a secret two levels under a non-sensitive key and one inside an
array element.

Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_0177mPHAdECD18nLLCTwR5rh
Signed-off-by: cliffhall <cliff@futurescale.com>

clients/cli/__tests__/servers-list.test.ts

@@ -226,6 +226,15 @@ describe("showServerEntry / servers/show", () => {
         // the whole value, not walk into it (#1910).
         "X-Api-Key": { primary: "sk-live-1", fallback: "sk-live-2" },
         nested: { keep: true },
+        // A secret buried under a non-sensitive key. A top-level-only check
+        // would print `accessToken` in full.
+        trace: {
+          id: "t-1",
+          accessToken: "sk-live-3",
+          deeper: { refresh_token: "sk-live-4", ok: 1 },
+        },
+        // Objects inside an array are reached too.
+        attempts: [{ password: "hunter2" }, { attempt: 2 }],
       },
       env: [
         { key: "TOKEN", value: "secret" },
@@ -250,8 +259,15 @@ describe("showServerEntry / servers/show", () => {
       Authorization: "[redacted]",
       "X-Custom": "ok",
       "X-Api-Key": "[redacted]",
-      // A structured value under a non-sensitive key survives intact.
+      // A structured value under a non-sensitive key survives intact...
       nested: { keep: true },
+      // ...but a sensitive key nested inside one does not.
+      trace: {
+        id: "t-1",
+        accessToken: "[redacted]",
+        deeper: { refresh_token: "[redacted]", ok: 1 },
+      },
+      attempts: [{ password: "[redacted]" }, { attempt: 2 }],
     });
     expect(sanitized.env).toEqual([
       { key: "TOKEN", value: "[redacted]" },