COD-105 discover + attach existing remote tmux sessions (detach-not-kill)

Phase 2 of the remote-tmux arc. Discover codeman-* tmux sessions already
running on a remote host (created by the remote's own Codeman or another
instance) and attach to one this Codeman didn't launch, with detach-not-kill
ownership for non-owned sessions.

- remote-hosts.ts: listRemoteCodemanSessions (ssh, VITEST-guarded, never throws)
  + pure parseRemoteSessionList + buildRemoteListSessionsCommand. Parser splits
  on the LITERAL \t the remote tmux emits (next-3.7 does not expand \t) AND a
  real tab. toAttachedSessionRemote builds a non-owned SessionRemote; toSessionRemote
  now marks the COD-104 launch path owned:true.
- tmux-manager.ts: buildRemoteAttachCommand (sibling of buildRemoteLaunchCommand);
  buildRemoteSessionCommand selects attach vs launch by ownership. killSession gains
  a detach-not-kill early return for non-owned remote sessions: tears down only the
  LOCAL pane (kills local ssh -> remote attach detaches), NEVER issues a remote
  kill-session.
- types/session.ts: RemoteSessionInfo; SessionRemote.owned + remoteSessionName.
- schemas.ts: CreateSessionSchema.attachRemoteSession {hostId, remoteSessionName};
  fixed a pre-existing no-useless-escape lint error in the jumpHost regex.
- case-routes.ts: GET /api/remote-hosts/:hostId/sessions (explicit discovery).
- session-routes.ts: attachRemoteSession create path -> non-owned session.
- UI (index.html/session-ui.js/styles.css): explicit "Discover existing sessions"
  button + Attach action (owned:false). No auto-discover.

Verified on aa-desktop: discovered codeman-disco1, attached (attached=1, shared
view), killed local probe pane -> remote SURVIVED_DETACH (attached=0). Tests:
parse/attach-cmd/ownership unit + discovery route, session-routes + case-routes green.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>
(cherry picked from commit 55f5ada9db6d01518a4adf6b752e460b5df39524)

src/web/schemas.ts

@@ -192,6 +192,22 @@ export const CreateSessionSchema = z.object({
     .max(100)
     .regex(/^[a-f0-9-]+$/, 'resumeSessionId must be a valid UUID')
     .optional(),
+  /**
+   * COD-105 — attach to an EXISTING remote tmux session discovered via
+   * `GET /api/remote-hosts/:hostId/sessions` (one this Codeman didn't create).
+   * The resulting session is NON-owned (closing it detaches, never kills the
+   * remote). `remoteSessionName` is a discovered `codeman-*` tmux session name.
+   */
+  attachRemoteSession: z
+    .object({
+      hostId: z.string().min(1).max(200),
+      remoteSessionName: z
+        .string()
+        .min(1)
+        .max(200)
+        .regex(/^codeman-[a-zA-Z0-9._-]+$/, 'remoteSessionName must be a codeman-* tmux session name'),
+    })
+    .optional(),
 });
 
 /**