test(ios): ClientTLS coverage 55.76% -> 89.49%, gate it, fix the three dead CI legs

ClientTLS was the most security-sensitive package in the tree and the least
covered, and it was not in the coverage gate at all (the gate's 4-package set
predates it). 48 -> 84 tests against the real macOS keychain, serialized with a
custom Testing trait after a @globalActor proved insufficient (actors yield at
await, so cross-await critical sections got interleaved by other cases' cleanup).

CI: the app/ipad/ios17 legs ran a bundle containing LiveServerSmokeTests, which
spawns tsx, with no npm ci -- a hard failure, not a skip, on a bare checkout.
Adds the missing iPad UI-test leg, and makes a missing iOS 17 runtime fail loudly
instead of silently reporting green.

ios/Packages/ClientTLS/Tests/ClientTLSTests/KnownGoodCSRVector.swift

@@ -0,0 +1,70 @@
+import Foundation
+import Security
+@testable import ClientTLS
+
+/// B4 · A KNOWN-GOOD PKCS#10 vector produced by OpenSSL, used to pin the
+/// hand-written DER encoder in `CertificateSigningRequest` byte-for-byte.
+///
+/// The ECDSA signature is randomized, so the stable part of a CSR is its
+/// `CertificationRequestInfo` — for a fixed key + fixed subject it is fully
+/// deterministic. That is what is pinned here: if our encoder ever drifts (a
+/// non-minimal length, a PrintableString instead of UTF8String, a wrong curve
+/// OID, an attributes SET that is not `A0 00`), the bytes stop matching
+/// OpenSSL's and this test fails.
+///
+/// Regenerate (OpenSSL 3.0.18, 2026-07-30):
+///   openssl ecparam -name prime256v1 -genkey -noout -out fixed.key.pem
+///   openssl req -new -key fixed.key.pem -subj "/CN=web-terminal-device" \
+///     -outform DER -out csr.der
+///   # CertificationRequestInfo = the first child of the outer SEQUENCE:
+///   openssl asn1parse -inform DER -in csr.der -i    # → offset 3, hl 3, l 128
+///   dd if=csr.der bs=1 skip=3 count=131 | base64
+///   # private key as X9.63 (0x04||X||Y||K) for SecKeyCreateWithData:
+///   openssl ec -in fixed.key.pem -text -noout       # → pub(65) || priv(32)
+///
+/// SECURITY: `privateKeyX963Base64` is a THROWAWAY key generated solely for this
+/// vector. It protects nothing, is never enrolled, and is never written to a
+/// keychain (`SecKeyCreateWithData` keeps it in-process). Same convention as the
+/// embedded `device.p12` + passphrase in `ClientTLSFixtures`.
+enum KnownGoodCSR {
+    static let subjectCommonName = "web-terminal-device"
+
+    /// OpenSSL's `CertificationRequestInfo` DER for `privateKeyX963Base64` +
+    /// `CN=web-terminal-device` (131 bytes).
+    static let certificationRequestInfoBase64 = """
+    MIGAAgEAMB4xHDAaBgNVBAMME3dlYi10ZXJtaW5hbC1kZXZpY2UwWTATBgcqhkjOPQIBBggqhkjO\
+    PQMBBwNCAARiJ8iQGXzCgho1TRYPNNcnqtgK/mrsNf+CAvoPbSH+12v1Q2OfVRgVPVYeS2AO3y87\
+    Oel9Uxe2QsHluJnGoifSoAA=
+    """
+
+    /// `0x04 || X(32) || Y(32) || K(32)` — the format `SecKeyCreateWithData`
+    /// expects for an EC private key.
+    static let privateKeyX963Base64 = """
+    BGInyJAZfMKCGjVNFg801yeq2Ar+auw1/4IC+g9tIf7Xa/VDY59VGBU9Vh5LYA7fLzs56X1TF7ZC\
+    weW4mcaiJ9Ko07ifqUA6io//Czd0XRMztqg+nY0OJcA1Y1LwoBMBbA==
+    """
+
+    static var certificationRequestInfoDER: Data {
+        Data(base64Encoded: certificationRequestInfoBase64, options: .ignoreUnknownCharacters)!
+    }
+
+    /// The fixed key as a `P256HardwareKey`, in-process only (no keychain item).
+    static func fixedKey() throws -> SecureEnclaveKey {
+        let blob = Data(
+            base64Encoded: privateKeyX963Base64, options: .ignoreUnknownCharacters
+        )!
+        let attributes: [String: Any] = [
+            kSecAttrKeyType as String: kSecAttrKeyTypeECSECPrimeRandom,
+            kSecAttrKeyClass as String: kSecAttrKeyClassPrivate,
+            kSecAttrKeySizeInBits as String: 256,
+        ]
+        var error: Unmanaged<CFError>?
+        guard let key = SecKeyCreateWithData(blob as CFData, attributes as CFDictionary, &error)
+        else {
+            throw SecureEnclaveKeyError.keyGenerationFailed(
+                String(describing: error?.takeRetainedValue())
+            )
+        }
+        return SecureEnclaveKey(privateKey: key)
+    }
+}