fix(connector): make certificate pinning real; disable Nagle

Security: with --verify-hostname off (the default), the old NoVerify
verifier accepted ANY server certificate — the CA loaded from --tls-ca
was never consulted, so the documented pinning was a no-op and the
connection was trivially MITM-able. Replace it with PinnedCertVerifier:
the presented end-entity cert must be byte-identical to a cert in the
--tls-ca file (any cert in a multi-cert PEM matches, supporting
rotation). Signature validation now uses the ring provider's full
algorithm set instead of a hardcoded 3-scheme list. Empty PEM files
fail fast instead of failing closed per-handshake.

The --verify-hostname path is unchanged (WebPki root-store validation).

Also: the third argument of connect_async_tls_with_config is
tungstenite's disable_nagle flag, not a verification toggle — we were
passing verify_hostname there, leaving Nagle ON for default users. Pass
true unconditionally, and disable Nagle on the plain ws:// path too;
socktop exchanges small request/response frames where Nagle only adds
latency.

Client now consumes the connector via a dual path+version dep so these
fixes are in local builds and CI before the crates.io publish (cargo
strips the path on publish). Connector version -> 1.51.0.

Verified E2E: agent A's cert connects to agent A; agent B's cert
against agent A fails the handshake (the rpi-worker-1 wrong-PEM
scenario); --verify-hostname against a 127.0.0.1 SAN still connects.

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

README.md

@@ -475,7 +475,7 @@ socktop --tls-ca /path/to/agent/cert.pem wss://HOST:8443/ws
 Notes:
 - Do not copy the private key off the server; only the cert.pem is needed by clients.
 - When --tls-ca/-t is supplied, the client auto‑upgrades ws:// to wss:// to avoid protocol mismatch.
-- Hostname (SAN) verification is DISABLED by default (the cert is still pinned). Use `--verify-hostname` to enable strict SAN checking.
+- Hostname (SAN) verification is DISABLED by default; instead the client PINS the certificate: the agent must present a cert byte-identical to one in your `--tls-ca` file (expiry is ignored in this mode — you pinned that exact cert). Use `--verify-hostname` to switch to strict chain + SAN validation instead.
 - You can run multiple clients with different cert paths by passing --tls-ca per invocation.
 
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