feat(adopt): adopt tmux sessions a human started, in all three locations

A tmux session someone opened by hand (`tmux new -s work`, then `claude`, or
just a shell) is invisible to Codeman: it lives on the default socket, not the
instance-scoped one Codeman owns. The home screen now lists those, and one
click wraps one in a Codeman tab. Local, in-container and over-ssh all work.

The shape is a WRAPPER session, not a direct attach: adoption creates an
ordinary `codeman-<8hex>` session on our own socket whose pane runs the
attach. That makes "detach, never kill the foreign session" structural rather
than a matter of discipline — `killSession` can only ever reach our own
wrapper, so no shape of caller bug reaches the foreign server. View reclamation
differs by location: local relies on client death and ssh on SIGHUP, but a
`docker exec` does NOT die with its client, so the in-container view has to be
reclaimed explicitly on kill or every adoption leaks one.

Measured facts, recorded in the code comments:

- A grouped session (`new-session -t`) buys `status off` and an independent
  current window. It does NOT buy an independent size. A window is one object
  with one size and a group shares it: on tmux 3.3a a bare attach and a grouped
  attach both shrink a 200x49 target to 80x23. Only `window-size largest` holds
  it, and that is a shared window option which survives our detach, so setting
  it would permanently rewrite the owner's configuration. Left unset.
- Session names come from other people, while the local launch chain ends in
  `bash -c` + `JSON.stringify`, which escapes neither `$` nor backticks — the
  outer shell performs command substitution before the inner single quotes are
  considered (verified: both substitutions inside the inner quotes ran). So
  session names and socket paths go through a character allowlist and are
  dropped at DISCOVERY, which means a non-conforming candidate never gets an
  id and the adopt endpoint fails closed when it re-resolves.
- `pane_current_command` is `node` for both claude and codex, so the mode can
  only come from a bounded process-tree walk of `pane_pid`'s argv; anything
  unrecognized is treated as a shell.

An adopted session has to say no to every assumption that Codeman owns the
pane: respawn, Ralph, the orchestrator and hook waits all refuse. The hook
check runs BEFORE the mode check, because adoption asks who launched the
process and no mode can vouch for a workspace Codeman never touched. `paneExit`
is forced to unknown, since the pane runs `tmux attach` rather than the agent
and its exiting with 0 only means the connection ended. Reboot restore refuses
too: all Codeman ever had was an attach command, and replaying it would build a
connection to a foreign session a reboot has almost certainly taken with it,
while presenting whatever it lands on as a session we restored.

Adoption is admin-only under multi-user mode: adopting someone's shell is
equivalent to arbitrary host execution. Discovery is read-only, never creates a
session, and degrades to an empty list whenever a probe cannot reach its target.

src/web/server.ts

@@ -1821,13 +1821,20 @@ export class WebServer extends EventEmitter {
     this.runSummaryTrackers.set(session.id, summaryTracker);
     summaryTracker.recordSessionStarted(session.mode, session.workingDir);
 
-    // Set working directory for Ralph tracker to auto-load @fix_plan.md (not supported for external CLIs)
-    if (!isExternalCliMode(session.mode)) {
+    // Set working directory for Ralph tracker to auto-load @fix_plan.md (not supported for external CLIs).
+    // ⚠️ Also skipped for an ADOPTED session, and for two reasons: Ralph is refused
+    // for one anyway, and its `workingDir` is the FOREIGN pane's cwd — a path that
+    // need not exist on this host at all. Watching it logged a caught ENOENT on
+    // every in-container adoption (`watch '/workspace/pythonserver'`), which is
+    // noise pointing at a real category error rather than a real failure.
+    if (!isExternalCliMode(session.mode) && !session.isAdopted) {
       session.ralphTracker.setWorkingDir(session.workingDir);
     }
 
     // Start watching for new images in this session's working directory (if enabled globally and per-session)
-    if ((await this.isImageWatcherEnabled()) && session.imageWatcherEnabled) {
+    if ((await this.isImageWatcherEnabled()) && session.imageWatcherEnabled && !session.isAdopted) {
+      // Same reason as the Ralph watcher above: an adopted session's workingDir is
+      // an observation about ANOTHER host's (or container's) filesystem.
       imageWatcher.watchSession(session.id, session.workingDir);
     }
 
@@ -3524,6 +3531,14 @@ export class WebServer extends EventEmitter {
               // MuxSession.docker; state.json carries SessionState.docker), so recovery
               // rebuilds the `docker exec` launch instead of a broken local command.
               docker: muxSession.docker ?? savedState?.docker,
+              // Adoption metadata round-trips for the same reason remote/docker do,
+              // and one more: it is the ONLY thing that marks this session as
+              // wrapping a process Codeman never launched. Dropping it on recovery
+              // silently re-enabled respawn, Ralph and hook-backed waits against
+              // someone else's live tmux session after every server restart —
+              // measured, not hypothetical. The mux record is preferred because it
+              // is what `killSession`'s detach-not-kill guard already reads.
+              adopt: muxSession.adopt ?? savedState?.adopt,
               owner: recoveredOwner,
               // Tab lineage survives a restart. It is only decoration, so a parent
               // that did NOT come back is harmless: the frontend draws an edge only