feat: session-scoped client integration channel (publish + events)

[jesse23]

Summary

• Adds POST /s/:id/publish — accepts one-shot or streaming newline-delimited JSON; broadcasts each line to subscribers as a discrete WS frame as it arrives; 204 after publisher closes; 409 if PTY not running
• Adds ws /ws/:id/events — WebSocket subscribe endpoint; receives one JSON object per frame; WS close 4002 if PTY not running
• Renames PTY WebSocket from /ws/:id → /ws/:id/pty for consistency (server and client ship together, not a breaking change)
• Channel lifecycle is tied to the PTY — subscribers are closed alongside PTY clients on shell exit, session delete, or server stop
• session.subscribers is a separate Set<WebSocket> from session.clients (PTY); the two are fully independent

Spec / ADR

• SPEC: Client Integration
• ADR 025

Test plan

• 223 tests passing, 100% coverage on all tracked files
• POST /s/:id/publish — 404 unknown session, 400 wrong content-type, 409 no PTY
• /ws/:id/events — 4001 unknown session, 4002 no PTY, receives published events, multi-line delivers one frame per line, invalid JSON lines skipped, closed with 4001 on shell exit

🤖 Generated with Claude Code

[Copilot]

Pull request overview

Adds a session-scoped “client integration channel” alongside the existing PTY WebSocket, enabling external publishers (CLI/tools) to stream newline-delimited JSON events into a session while browser subscribers receive one JSON frame per event.

Changes:

• Added POST /s/:id/publish to stream/submit JSON lines and broadcast valid lines to session event subscribers.
• Added ws /ws/:id/events subscribe endpoint and introduced session.subscribers to manage subscriber lifecycle tied to the PTY.
• Renamed PTY WebSocket endpoint from /ws/:id to /ws/:id/pty and updated client/tests/docs accordingly.

Reviewed changes

Copilot reviewed 10 out of 10 changed files in this pull request and generated 5 comments.

Show a summary per file

File	Description
src/server/websocket.ts	Adds /events WebSocket routing, subscriber tracking, and subscriber cleanup on shutdown/exit.
src/server/websocket.test.ts	Updates PTY WS route and adds tests for the new events subscription behavior.
src/server/session.ts	Extends Session with subscribers: Set<WS> and initializes it.
src/server/routes.ts	Implements POST /s/:id/publish streaming JSON-line ingestion and broadcasting.
src/server/routes.test.ts	Adds route-level tests for /s/:id/publish error cases.
src/client/index.ts	Updates browser client to connect to /ws/:id/pty.
src/cli/http.test.ts	Adds CLI tests around executor selection and spawn error handling.
docs/specs/webtty.md	Documents the client integration feature in the feature table.
docs/specs/client-integration.md	Adds the client integration spec document.
docs/adrs/025.server.channel.md	Adds the ADR describing the integration channel API and lifecycle.

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