fix(auth): address Copilot review round 17

Three findings. The first is the fourth consecutive one in the refresh path,
so it is answered by making that path testable rather than by patching it
again.

**The refresh-after-persist wiring was covered by nothing.** It lived as two
inline `await …; refresh()` pairs in `App.tsx`, which is deliberately outside
the coverage `include` — so the hook's tests and the modals' tests could both
pass while the callback joining them was broken, leaving the security footer
stale after exactly the write that changed it. Three of the last four rounds
found defects in this path; none of them could have been caught by a test,
because there was nowhere for one to live.

Extracted to `utils/refreshingPersist`, which is inside the gate and has its
own tests: refresh runs after the persist resolves (not before — refreshing
first re-reads the descriptor the pending write is about to invalidate),
arguments pass through unchanged (the server-settings caller is
`(id, settings)`, and a transparent wrapper is the difference between saving
the entry and dropping it), and a failed persist refreshes nothing while
propagating the error.

**A tmpfs-style false promise, in the path fallback.** With neither `HOME`
nor `USERPROFILE` set — an ordinary service environment —
`defaultSecretFilePath` returned `.mcp-inspector/secrets.json`, a *relative*
path, while `FileSecretStoreOptions.filePath` and the `SecretStorageInfo.path`
the footer offers to copy both promise an absolute one. Resolved like the two
override branches above it.

**A warning that was usually false.** The session-store notice fired on every
`/api/servers` read whenever the store was in-memory — including for the
default empty catalog, where "plaintext values are left on disk" is not true
of anything, repeated on every list refresh. It is now emitted lazily, at most
once per server instance, and only when the loop actually preserves a
non-empty secrets set. A log line that is usually untrue is one people learn
to skip, which costs it the occasion it matters.

The remaining suppressed comment is the hand-off's check-to-delete race,
tracked in #2082.

Full `npm run ci` green.

Signed-off-by: cliffhall <cliff@futurescale.com>

core/auth/node/secret-store-selection.ts

@@ -117,7 +117,13 @@ export function defaultSecretFilePath(): string {
   const storageDir = process.env[STORAGE_DIR_ENV]?.trim();
   if (storageDir) return path.resolve(storageDir, "secrets.json");
   const homeDir = process.env.HOME || process.env.USERPROFILE || ".";
-  return path.join(homeDir, ".mcp-inspector", "secrets.json");
+  // Resolved like the two override branches. A service started with a minimal
+  // environment has neither variable, and the `"."` fallback then yields
+  // `.mcp-inspector/secrets.json` — a *relative* path, while
+  // `FileSecretStoreOptions.filePath` and the `SecretStorageInfo.path` the UI
+  // copies both promise an absolute one. The footer would offer to copy a
+  // location that means nothing without knowing the process's cwd.
+  return path.resolve(homeDir, ".mcp-inspector", "secrets.json");
 }
 
 /**