COD-107 remote SSH: custom port + advanced connection options (escape hatch)

The Remote case form could only reach port-22, default-identity, directly
SSH-able hosts. Add an escape-hatch set of SSH connection options so Codeman
can reach a host like aa-desktop (custom port 2222, ed25519 identity, cloudflared
SOCKS5 ProxyCommand) the way ssh-aa-desktop does — without shelling out to that
wrapper.

- Model (types/session.ts): new optional RemoteSshOptions (identityFile,
  socksProxy, jumpHost, extraSshOptions) on RemoteHost AND SessionRemote; all
  absent = today's behavior. toSessionRemote() carries them case->session.
- Shared buildSshConnectionArgs(remote) in remote-hosts.ts: pure, exported,
  ordered ssh connection tokens (-o BatchMode=yes, -p, -i <abs identity with
  ~/$HOME expanded + shellescaped>, -J, -o ProxyCommand=nc -X 5 -x <socks>
  %h %p emitted as ONE shellescaped token so %h %p reach ssh literally, then
  each extraSshOptions -o). Both buildRemoteLaunchCommand (tmux-manager.ts) and
  buildRemoteTmuxCheckCommand now use it, so the prereq probe and the real
  launch connect identically. checkRemoteTmuxAvailable widened to accept the
  options (callers already pass the full host).
- Validation (schemas.ts): identityFile (no newline/NUL), socksProxy
  (host:port), jumpHost (no shell metachars), extraSshOptions (KEY=VALUE,
  reject newline/NUL/backtick/$() — defense-in-depth on operator-entered config.
- UI (index.html + session-ui.js): SSH Port field + collapsible "Advanced SSH"
  section (identity, SOCKS proxy, jump host, extra -o options one per line);
  wired into the remote-host create payload.

Empty-options remotes emit byte-identical ssh to before (pinned by test).

Tests: test/remote-ssh-options.test.ts (buildSshConnectionArgs +
buildRemoteLaunchCommand + buildRemoteTmuxCheckCommand for the aa-desktop set,
escaping/%h %p/identity-~ expansion, byte-identical back-compat); case-routes
schema tests (advanced options round-trip; malformed extraSshOptions/socksProxy
rejected). tsc/eslint/frontend-syntax/prettier/build clean.

Acceptance (real remote, no wrapper): the emitted command connected to
aa-desktop through the cloudflared SOCKS proxy and created a durable remote
tmux session (verified independently via ssh-aa-desktop: CONNECTED_NO_WRAPPER,
STILL_ALIVE_AFTER_DETACH); checkRemoteTmuxAvailable over the proxy returned
{ok:true, tmuxPath:/usr/local/bin/tmux}; test session cleaned up.

src/types/session.ts

@@ -45,7 +45,34 @@ export type SessionMode = 'claude' | 'shell' | 'opencode' | 'codex' | 'gemini';
 
 export type RemoteCommandMode = Extract<SessionMode, 'shell' | 'claude' | 'opencode' | 'codex' | 'gemini'>;
 
-export interface RemoteHost {
+/**
+ * Advanced SSH connection options shared by RemoteHost and SessionRemote.
+ *
+ * COD-107 — all fields are optional; every field absent reproduces today's
+ * behavior (port-22, default-identity, directly-SSH-able hosts). These describe
+ * HOW Codeman reaches the host (identity, proxy, jump host, arbitrary `-o`),
+ * letting it connect to e.g. a host fronted by a cloudflared SOCKS5 proxy on a
+ * custom port — the same connection `ssh-aa-desktop` makes — without a wrapper.
+ */
+export interface RemoteSshOptions {
+  /**
+   * Path to an SSH identity (private key) file — path ONLY, never key bytes.
+   * A leading `~`/`$HOME` is expanded to an absolute path at command-build time
+   * (ssh does not expand `~` in `-i`).
+   */
+  identityFile?: string;
+  /**
+   * SOCKS5 proxy as `host:port` (e.g. `127.0.0.1:1080`). Expands to
+   * `-o ProxyCommand=nc -X 5 -x <host:port> %h %p` (the cloudflared/SOCKS5 case).
+   */
+  socksProxy?: string;
+  /** SSH jump host (`[user@]host[:port]`) emitted as `-J <jumpHost>`. */
+  jumpHost?: string;
+  /** Arbitrary additional `-o KEY=VALUE` options (escape hatch). Each `KEY=VALUE`. */
+  extraSshOptions?: string[];
+}
+
+export interface RemoteHost extends RemoteSshOptions {
   id: string;
   label: string;
   host: string;
@@ -61,7 +88,7 @@ export interface RemoteCase {
   remotePath: string;
 }
 
-export interface SessionRemote {
+export interface SessionRemote extends RemoteSshOptions {
   hostId: string;
   label: string;
   host: string;