fix: keep an adopted session off the direct-PTY fallback (release review)

A wrapper that could not start fell back to a direct PTY: `claude
--dangerously-skip-permissions` or a server-account shell in /tmp on this
host, under a tab still carrying the foreign session's name, so someone who
opened an ssh or container session ended up typing into this machine.

startInteractive and startShell now fail the start for an adopted session
and leave `_useMux` on, so selecting the tab tries the wrapper again. The
`error` event carries the reason, since the browser's re-attach does not
read the route's answer. A session with no mux at all is refused the same
way.

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

docs/api-reference.md

@@ -1188,9 +1188,11 @@ session: respawn, Ralph (its config and the `fix-plan/write`, `fix-plan/read` an
 `ralph-prompt/write` file routes), auto-clear, auto-compact, auto-resume, custom model
 endpoints, prompt uploads and the image watcher. `stop` waits are a 400, and so are
 `blocked` waits unless Codeman reads that CLI's dialogs off its screen (codex), the git
-routes answer `unsupported` with `reason: "adopted"`, and `last-response` answers empty,
-since Codeman knows no transcript for it. Its `paneExit` stays absent, because the pane
-holds a `tmux attach` and not the agent. Reboot restore does not rebuild one.
+routes answer `unsupported` with `reason: "adopted"`, and
+`last-response` answers empty, since Codeman knows no transcript for it. Its `paneExit`
+stays absent, because the pane holds a `tmux attach` and not the agent. Reboot restore
+does not rebuild one. A wrapper that cannot start answers `OPERATION_FAILED` and leaves
+the tab to be tried again: Codeman never starts a local process in its place.
 
 ## Approvals Inbox
 

docs/architecture-invariants.md

@@ -109,7 +109,7 @@ Input arriving during a wake is buffered: a chunk over 4 KB is dropped whole, ne
 
 **No workspace.** ⚠️ An adopted session keeps its connection on `adopt.remote`/`adopt.docker`, so `session.remote` and `session.docker` are undefined, and its `workingDir` is the neutral `/tmp`. Code that branches on those two reads an in-container or over-ssh adoption as a local session working in `/tmp`. So anything that treats `workingDir` as the session's workspace must also test `session.isAdopted` (`adopt` on a pure view): uploads, the upload GC, git status, git fetch and its scheduler, the image watcher, Read My Mind's git signals, the Discord folder, `last-response`, guarded input and Ralph's `@fix_plan.md` and `@ralph_prompt.md` routes all do. The file surfaces (Files panel, File Viewer and its edit mode) still treat `/tmp` as the workspace, which is harmless: it is world-writable anyway, and adoption is admin-only in multi-user mode. A wrapper reports `statusLineExporter: 'remote'`, which is also what keeps keep-warm off it.
 
-**Lifecycle.** `paneExitApplies` is false for a wrapper, so an attach that ended is never `paneExit` and the sweep never closes the tab. Boot recovery re-attaches a dead wrapper, which prints that the session is gone and exits. Reboot restore refuses one, since all Codeman ever had was an attach command.
+**Lifecycle.** `paneExitApplies` is false for a wrapper, so an attach that ended is never `paneExit` and the sweep never closes the tab. Boot recovery re-attaches a dead wrapper, which prints that the session is gone and exits. Reboot restore refuses one, since all Codeman ever had was an attach command. ⚠️ A wrapper that cannot start fails the start, and selecting the tab tries it again (`_failAdoptedStart()`). It never takes the direct-PTY fallback, which would run a new local `claude --dangerously-skip-permissions` or a server-account shell in `/tmp` under the foreign session's name.
 
 ### Docker cases