OAuth: re-key store to (server, issuer) + SEP-837/2350/2352 auth UX (#1694)

* OAuth: re-key store to (server, issuer) + SEP-837/2350/2352 auth UX (#1625)

Re-key the persisted OAuth store to (server, issuer) and add the
SEP-837/2350/2352 authorization-hardening UX. The SDK v2 auth() drives the
SEP-2352 flow off the provider's ctx.issuer; the Inspector's job is to honor it
and round-trip the issuer stamp.

SEP-2352 — issuer-bound credentials
- ServerOAuthState nests issuer-bound credentials under
  byIssuer[issuer] = { clientInformation, clientRegistrationKind, tokens }, with
  an activeIssuer pointer answering the transport's ctx-less per-request bearer
  read.
- Fix a latent bug: OAuthStorageBase re-parsed tokens/client-info through
  OAuthTokensSchema/OAuthClientInformationSchema, which strip the non-RFC
  `issuer` field and silently defeat the SDK's discardIfIssuerMismatch. The
  store re-attaches the stamp from the byIssuer key.
- BaseOAuthClientProvider threads ctx.issuer and implements
  discoveryState()/saveDiscoveryState() (activates the SDK's callback-leg
  AuthorizationServerMismatchError binding check) and invalidateCredentials().
- Lazy, migration-free upgrade: a legacy pre-1625 blob's top-level
  clientInformation/tokens are returned as an unkeyed fallback until the first
  issuer-stamped save promotes them into byIssuer.

SEP-837 — application_type
- DCR declares application_type: "native" (localhost Inspector).
- ClientSettingsForm renders RegistrationRejectedError detail and reflects DCR's
  deprecated-in-favor-of-CIMD (SEP-991) status.

SEP-2350 — step-up scope union
- Per-server onInsufficientScope (reauthorize | throw) setting wired
  ServerSettingsForm -> StoredMCPServer.oauth -> StreamableHTTPClientTransport.
- StepUpAuthModal visualizes the prior-union-challenged scope set, tagging each
  scope `new` vs `already granted`.

mcpAuth simplification
- Delete the hand-rolled authorizeWithoutRefresh (mishandled issuer stamping);
  forward forceReauthorization/skipIssuerMetadataValidation to native SDK auth()
  so both the initial and step-up paths get SEP-2352 stamping.

Vocabulary + docs
- OAuthStep gains cimd_fetch / issuer_comparison / scope_step_up (recorded on a
  step-up redirect); the Network tab labels auth requests by OAuth phase.
- v2_auth_hardening.md gains an as-built status section.

Deferred to the era-aware card: the SdkError(EraNegotiationFailed) ->
UnauthorizedError unwrap and finishAuth(URLSearchParams) form (only fire under
non-legacy negotiation).

Closes #1625

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

* Address @claude review: issuer-stamp source gating + clear/activeIssuer + phase over-match

- SEP-2352: stamp the issuer only when the credential actually came from the
  byIssuer slot (`fromSlot`), not merely when a slot exists. A partially-populated
  slot alongside a surviving legacy field would otherwise stamp a legacy (possibly
  cross-AS) credential with the current issuer, defeating discardIfIssuerMismatch.
- Issuer-scoped clears no longer promote the cleared issuer to `activeIssuer`
  (updateIssuerSlot gains a `setActive` flag; save paths keep the promotion).
- oauthNetworkPhase matches register/token/authorize as the final path segment
  (trailing slash tolerated) so `/token/refresh` or `/api/register/foo` no longer
  over-match.
- Tests for all three.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

---------

Co-authored-by: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

clients/web/src/test/integration/mcp/remote/servers-route.test.ts

@@ -1478,6 +1478,67 @@ describe("/api/servers routes", () => {
       expect(body.error).toMatch(/settings\.env/);
     });
 
+    it("rejects an invalid settings.oauthOnInsufficientScope with 400", async () => {
+      writeFileSync(
+        h.configPath,
+        JSON.stringify({
+          mcpServers: {
+            srv: { type: "streamable-http", url: "https://x.test/mcp" },
+          },
+        }),
+      );
+      const res = await fetch(`${h.baseUrl}/api/servers/srv`, {
+        method: "PUT",
+        headers: { "Content-Type": "application/json" },
+        body: JSON.stringify({
+          settings: {
+            headers: [],
+            metadata: [],
+            connectionTimeout: 0,
+            requestTimeout: 0,
+            env: [],
+            oauthOnInsufficientScope: "nope",
+          },
+        }),
+      });
+      expect(res.status).toBe(400);
+      const body = (await res.json()) as { error?: string };
+      expect(body.error).toMatch(/oauthOnInsufficientScope/);
+    });
+
+    it("persists a valid settings.oauthOnInsufficientScope onto the stored config", async () => {
+      writeFileSync(
+        h.configPath,
+        JSON.stringify({
+          mcpServers: {
+            srv: { type: "streamable-http", url: "https://x.test/mcp" },
+          },
+        }),
+      );
+      const res = await fetch(`${h.baseUrl}/api/servers/srv`, {
+        method: "PUT",
+        headers: { "Content-Type": "application/json" },
+        body: JSON.stringify({
+          settings: {
+            headers: [],
+            metadata: [],
+            connectionTimeout: 0,
+            requestTimeout: 0,
+            env: [],
+            oauthOnInsufficientScope: "throw",
+          },
+        }),
+      });
+      expect(res.status).toBe(200);
+      const stored = JSON.parse(readFileSync(h.configPath, "utf-8")) as {
+        mcpServers: Record<
+          string,
+          { oauth?: { onInsufficientScope?: string } }
+        >;
+      };
+      expect(stored.mcpServers.srv?.oauth?.onInsufficientScope).toBe("throw");
+    });
+
     it("ignores settings env/cwd for a non-stdio server (no leak onto config)", async () => {
       writeFileSync(
         h.configPath,