fix(web): defer issuer validation to onBlur, block silent-drop on close, require a real host URL (closes #1544) (#1545)

* fix(web): defer IdP issuer URL error to onBlur in Client Settings (#1544)

The Enterprise-Managed Authorization Issuer field validated its URL inline on
every render, so the 'Must be an http(s) URL' error nagged while the user was
still mid-typing (e.g. before 'https:/…' is complete).

Gate the issuer error display on an issuerTouched flag set onBlur; once
touched it tracks the value live, so the error clears as soon as a valid URL
is entered. The persist gate (canPersistClientSettingsDraft → validateClientSettings)
is unchanged and still validates independently, so an invalid issuer is never
written to the backend regardless of touched state.

Closes #1544

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

* fix(web): reveal issuer error and block close on invalid issuer (#1544)

Extend the on-blur deferral so an invalid issuer can't be silently dropped on
modal close (the auto-save flush would otherwise discard it with no feedback).

ClientSettingsModal now intercepts its close (X / Esc / overlay): if the issuer
is invalid it reveals the field error (via the form's revealIssuerError prop,
overriding on-blur gating) and keeps the modal open instead of closing. The
user can fix the URL or clear the field — an empty issuer is valid to leave.
The block lives in the modal (unit-tested) rather than App, so App.tsx stays a
thin flush+close that only runs when the close is allowed; the persist gate is
unchanged. Reveal state resets via the modal's open/close remount key.

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

* fix(core): require a real host in isAbsoluteHttpUrl, not just an http(s) scheme (#1544)

The issuer validation used URL.canParse + an http(s) protocol check, which the
WHATWG parser accepts for bare/degenerate values that aren't actually usable
URLs — e.g. https://foo, https://example, https://. , https://.. all passed.

Tighten the shared rule (used by both the Zod config schema and the form's
inline validation): after parsing and the http(s) scheme check, require the
host to actually look like a host — localhost, an IPv6 literal, or a dotted
domain/IPv4 with at least two non-empty labels. Single-label, bare-dot, and
empty-label hosts are now rejected. Add core tests for the accepted
(dotted/IPv4/IPv6/localhost) and newly-rejected cases.

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/App.tsx

@@ -2377,6 +2377,9 @@ function App() {
     );
 
   const onClientSettingsModalClose = useCallback(() => {
+    // Only fires when ClientSettingsModal allows the close (it blocks on an
+    // invalid issuer and reveals the error instead). The implicit "save" is the
+    // flush below; the persist gate drops anything still incomplete.
     flushClientSettingsDraft();
     setClientSettingsOpen(false);
   }, [flushClientSettingsDraft]);