fix: adopted tmux targets, hung servers and the attach chain (release review)

Names tmux reads as target syntax (`@1`, `%1`, `=eq`, a bare `~`) passed the
has-session guard by name and then joined something else in new-session -t:
another session, or a fresh shell on the foreign server. They are refused at
discovery now, and take the existing skipped note.

One stopped tmux server emptied the whole local list and left a stuck client
per scan. Each server now gets a bounded ping with stdout at /dev/null first,
because a tmux client hands dups of its stdout to the server: a stopped server
holds our pipe open after the client is dead, so a watchdog around list-panes
cannot work. The probe runs in its own process group, all three transports
keep the rows read before a failure, and a missed ping becomes a note.

The attach and the probe pass -u, so a POSIX-locale container no longer garbles
the tab or lists a non-ASCII name as underscores. A docker attach gets the same
TERM and COLORTERM an owned container's exec gets.

A missing tmux no longer reads as "session is gone", and the launch line's `$`
now reaches bash unexpanded, so the ssh attach's PATH line is expanded at the
far end, as the probe's already was.

fix-plan/write, fix-plan/read and ralph-prompt/write refuse an adopted session:
its workingDir is the neutral /tmp, so they read and wrote a predictable name
in a folder anyone can write to.

FOREIGN_MAX_SOCKETS is gone: it capped nothing, and a real cap in glob order
would never reach `default` on a box with many `codeman-*` sockets (this one
has 212). Closing an adopted tab re-reads the outside-sessions list.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

src/web/public/app.js

@@ -10879,6 +10879,9 @@ class CodemanApp {
       // An SSE resync (handleInit) that landed mid-request rebuilds the list from
       // the server, which still had the session then.
       if (this.sessions.has(sessionId)) this._onSessionDeleted({ id: sessionId });
+      // The home screen read the outside-sessions list when the tab went, before this
+      // delete landed, so its row would say "Go to tab" with no tab until the next poll.
+      if (session?.adopt) void this.loadForeignSessions?.();
       if (killMux) {
         this.showToast('Session closed and tmux killed', 'success');
       } else {

src/web/routes/ralph-routes.ts

@@ -37,6 +37,15 @@ import type { SessionPort, EventPort, RespawnPort, ConfigPort, InfraPort } from
 /** Cap on a remote `@fix_plan.md` read over ssh (a task list, not a document). */
 const MAX_REMOTE_FIX_PLAN_BYTES = 1024 * 1024;
 
+/**
+ * An adopted session's `workingDir` is the neutral wrapper folder `/tmp`, not a workspace.
+ * Using it would write a predictable name into a folder anyone can write to, and read one
+ * back, while the agent in the pane never sees either file.
+ */
+function refuseAdoptedRalphFile(file: string) {
+  return createErrorResponse(ApiErrorCode.INVALID_INPUT, `${file} is not available for an adopted session`);
+}
+
 export function registerRalphRoutes(
   app: FastifyInstance,
   ctx: SessionPort & EventPort & RespawnPort & ConfigPort & InfraPort
@@ -208,6 +217,7 @@ export function registerRalphRoutes(
   app.post('/api/sessions/:id/fix-plan/write', async (req) => {
     const { id } = req.params as { id: string };
     const session = findSessionOrFail(ctx, id, req);
+    if (session.isAdopted) return refuseAdoptedRalphFile('@fix_plan.md');
     // A remote session's workingDir is a path on the remote host. Writing it with local fs would land
     // the file in a same-named local folder (or fail), and remote writes are out of scope by design
     // (src/remote-files.ts is read-only), so it is refused, like the File Viewer's remote edit.
@@ -244,6 +254,7 @@ export function registerRalphRoutes(
   app.post('/api/sessions/:id/fix-plan/read', async (req) => {
     const { id } = req.params as { id: string };
     const session = findSessionOrFail(ctx, id, req);
+    if (session.isAdopted) return refuseAdoptedRalphFile('@fix_plan.md');
 
     const workingDir = session.workingDir;
     if (!workingDir) {
@@ -291,6 +302,7 @@ export function registerRalphRoutes(
     const { id } = req.params as { id: string };
     const { content } = parseBody(RalphPromptWriteSchema, req.body, 'Invalid request body');
     const session = findSessionOrFail(ctx, id, req);
+    if (session.isAdopted) return refuseAdoptedRalphFile('@ralph_prompt.md');
     // Same rule as fix-plan/write: never write a remote session's file on the local disk.
     if (session.remote) {
       return createErrorResponse(