feat(docker): attach a case to an already-running container

Docker cases could only run in a container Codeman created itself. Attaching to
one the user already built and runs means Codeman must leave that container's
lifecycle completely alone, which the launch chain could not do: it was
`image inspect` -> `inspect || create` -> `start` -> `exec`.

Adds `DockerCase.owned`, mirroring the `owned:false` contract remote-SSH already
uses for attached sessions. Absent (every existing case) means owned, so current
behaviour is byte-identical. `false` means the container belongs to the user and
Codeman may only exec into it.

The launch chain for an attached container only looks, then execs: no image gate
(the image is theirs), no create, and no `start` — starting a container we do not
own is the very mutation attaching promises not to perform. A missing or stopped
container fails closed with an actionable message instead. Credential seeding is
skipped too: those copies read from create-time read-only mounts that do not
exist here, and writing host credentials into someone's container is not ours to
do, so its CLIs must already be authenticated inside it.

Four fail-closed guards. buildDockerStopCommand and buildDockerRemoveCommand
throw during pure string construction, so no caller bug can turn into a
`docker stop`/`rm` on a container we do not own; removeDockerContainer refuses
again at the lowest layer; drift reports "none" for an attached container, which
carries no `codeman.confighash` label and would otherwise always look drifted and
409 the launch gate forever; and the orphan reaper skips attached containers
through a check deliberately independent of the two conditions already covering
them.

`owned` is applied AFTER the config hash is computed. dockerConfigHash takes an
explicit field list, so ownership can never shift an existing case's hash — if it
did, every pre-existing case would trip the drift gate at once, and the remedy
the UI offers is "recreate the container".

Adds POST /api/cases/docker-adopt and a read-only
POST /api/docker-cases/adopt-preflight. The preflight refuses at LINK time rather
than at session launch, where the only ways out would be a dead pane or starting
a container we do not own.

Tests assert the negative guarantee directly — that create, start, stop, rm,
restart and kill are absent from the generated commands while `docker exec -it`
and `new-session -A` remain — since it cannot be observed by using the feature.

src/types/session.ts

@@ -243,6 +243,24 @@ export interface DockerCase {
   containerWorkdir?: string;
   /** Container name (default codeman-case-<slug>). */
   container?: string;
+  /**
+   * Whether THIS Codeman created the container (mirror of `SessionRemote.owned`).
+   *
+   * - `true` (default for cases Codeman linked/quick-created): we own the
+   *   container; drift may recreate it, case-delete may `docker rm -f` it, and
+   *   the launch chain may create + start it.
+   * - `false` (ADOPTED: an already-running container the user built and runs
+   *   themselves): Codeman must never create, start, stop, restart or remove it.
+   *   The launch chain fails closed when the container is missing or not running
+   *   instead of touching its lifecycle, drift is not evaluated (there is no
+   *   `codeman.confighash` label to compare), and no credential seed is copied
+   *   into its HOME. Only the in-container tmux session is ever created or
+   *   killed — exactly the `owned:false` remote-SSH contract.
+   *
+   * Absent is treated as owned (cases persisted before this field existed were
+   * all created by us).
+   */
+  owned?: boolean;
   /** Last captured Claude conversation id, replayed via --resume on a fresh launch. */
   lastClaudeSessionId?: string;
 }
@@ -275,6 +293,12 @@ export interface SessionDocker {
   extraExecArgs?: string[];
   /** Stable hash of the drift-relevant create args (recreate-on-drift detection). */
   configHash?: string;
+  /**
+   * Mirror of `DockerCase.owned`, flattened onto the live session so every
+   * lifecycle decision (launch chain, drift, stop, remove) can see it without
+   * re-reading docker-cases.json. Absent = owned. See `DockerCase.owned`.
+   */
+  owned?: boolean;
 }
 
 /**