id(world): terminal shells send frames the host refuses (found by the F13.1 shell-contract check) #836

What

The first run of the new shell-contract conformance check (F13.1, #783) found three places where the terminal shells send frames the host refuses. Each passed the code review that created it: nothing checked a shell against the protocol.

1. id world join --command-mode sends invalid frames. pump_command_frame (pkgs/id/src/commands/world.rs) sent /stats, /caps and /records without the required capability field, and /documents, /document, /logs and /help as frame types that do not exist (documents, document, logs, help). The host answers invalid world frame to every one of them.
2. /stats in an SSH cmd: session always fails. world_ssh sends {"type":"info","capability":…} from the joined session and has a renderer for the module_info reply. But handle_client_frame (pkgs/id/src/world_session/mod.rs) answers info with already joined, which also marks the SSH shell as errored. No test covered /stats.
3. A wide SSH terminal is refused a view. A pty wider than 500 columns or taller than 200 rows produces a resize outside the host's bounds, and the host answers with an error instead of a view. The browser clamps; SSH did not.

Fix (in the F13.1 PR on id/phase-13-impl)

• The pump fills in the session capability and answers local-only commands on stderr, so stdout stays a pure JSON frame stream. A test checks every frame it sends against the contract.
• The host answers info in the joined phase, authorized by the session's own capability, as it already does for records. The SSH cmd: e2e test now runs /stats.
• The SSH shell clamps resize to the contract bounds: width 1..=500, height 1..=200.

Refs #783.