fix(auth): keep the failure path total, and align the docs with the new order (#2144)

Copilot review round 14. Two code fixes and a documentation sweep.

- `buildRevocationRequest` ran outside `revokeToken`'s best-effort try.
  `encodeURIComponent` throws on a lone UTF-16 surrogate — valid JSON, so it
  can reach there from a persisted client id or secret — and every caller has
  already cleared its local state by then, so a rejection instead of a `failed`
  outcome would break the documented guarantee. Construction is inside the try
  now, and the catch reports `params.endpoint` rather than a `url` that may not
  exist on that path.
- The fixture's Basic decode turned a malformed percent escape into an Express
  500, reporting a bad credential as a server fault rather than as the
  `invalid_client` 401 the endpoint means. Decoding failure is failed
  authentication.
- Ten places still said revocation happens *before* the clear, which the
  reorder in the previous commit made false: the settings-form description, the
  `--no-revoke` help text, both READMEs, `docs/mcp-server-configuration.md`,
  three JSDoc blocks, and the PR body. Swept, and the ordering is stated where
  it is load-bearing rather than asserted in passing. Also merged the two
  adjacent JSDoc blocks on `InspectorClient.clearOAuthTokens`.

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>

test-servers/src/test-server-oauth.ts

@@ -802,8 +802,16 @@ async function authenticateRevocationClient(
     // server decodes each half after splitting on it. Decoding is what makes a
     // credential containing a reserved character (`:` in the id, `%` or `/` in
     // the secret) survive the round trip.
-    clientId = decodeURIComponent(decoded.slice(0, separator));
-    clientSecret = decodeURIComponent(decoded.slice(separator + 1));
+    //
+    // A malformed escape makes `decodeURIComponent` throw, which Express would
+    // turn into a 500 — so a bad credential would be reported as a server
+    // fault rather than as the `invalid_client` 401 this endpoint means.
+    try {
+      clientId = decodeURIComponent(decoded.slice(0, separator));
+      clientSecret = decodeURIComponent(decoded.slice(separator + 1));
+    } catch {
+      return null;
+    }
   } else {
     const bodyId: unknown = req.body?.client_id;
     const bodySecret: unknown = req.body?.client_secret;