let the pty sidecar decide what shell it runs

officer built the whole PtyInitConfig: it read the owner's SHELL (defaulting to
/bin/zsh), added `-i`, read their HOME, expanded `~` against it, and hardcoded
`host: true`. none of that is a proxy's business — the sidecar is the process that
calls pty.spawn, so it is the one that should know what to spawn and where.

the config now carries only what the bridge actually knows: sessionId, the folder
the panel was opened on, and the client's cols/rows. shell, args, home and cwd
resolution moved into the sidecar. home comes from HOME_DIR ?? HOME, mirroring
data-path.ts:getOwnerHomeDir — terminal was the one host-executing surface reading
process.env.HOME directly, which is identical here and divergent anywhere HOME_DIR
is set to something else.

deleted the bwrap sandbox branch rather than moving it. it was selected by
`config.host`, which officer hardcoded to true, so it never ran — and it expected
`shell` to contain a fully-built bwrap command that nothing on either side ever
built. it could not have worked. a terminal here is the owner's own shell on the
owner's own machine by design (platform/CLAUDE.md), so there is no jail to preserve.
its ensureUserFiles half duplicated api/users/provision.ts:seedShellConfigs, which
is the live seeder of those same templates and stays.

also deleted the 'cwd' handler that turned a message into `cd <path>\r` typed at
the shell. no frontend has ever sent that message — the browser composes its own cd
— so it was unreachable, and synthesizing keystrokes is not something a relay
should do.

the integration test pins SHELL and HOME_DIR now that the sidecar reads them, and
asserts the shell starts in the resolved `~` rather than officer having resolved it.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

src/servers/sidecar/protocol.ts

@@ -130,16 +130,15 @@ export type VncSessionInfo = {
 
 // ── PTY types ──
 
+// What officer knows about a terminal, and nothing more. The shell, its arguments, the home directory and
+// whether the shell is sandboxed are the sidecar's own decisions — they used to travel in here, which is
+// how officer ended up reading the owner's SHELL and HOME and hardcoding `host: true`.
 export type PtyInitConfig = {
   sessionId: string;
-  shell?: { command: string; args?: string[] };
+  /** The folder the panel was opened on. `~`, `~/x` and absolute paths only; resolved by the sidecar. */
   cwd?: string;
-  homeDir?: string;
-  userLabel?: string;
-  host?: boolean;
   cols?: number;
   rows?: number;
-  env?: Record<string, string>;
 };
 
 // PTY commands (API → PTY sidecar)