docs: update Run feature docs for the tmux+PTY terminal (was stream-json)

- README.md: replace stream-json bullet with tmux+PTY description
- ARCHITECTURE.md: update /run Workspace page section to reflect PTY transport, xterm.js, and ccam lanes shell
- docs/API.md: replace stream-json endpoint docs with /api/run/*+/ws-pty/:runId PTY endpoint docs
- docs/LANES.md: add "Attaching a real terminal to a lane" section for ccam lanes shell; update lane "start" action docs and /run Workspace description
- Remove stale references: run_stream, run_input_ack, conversation/headless modes, RunConsole components

README.md

@@ -15,8 +15,10 @@ Internal build — all rights reserved.
 - **Stage detection.** The stage is inferred from the tool stream, so a session
   that never calls `ccam stage` still shows progress — rendered dashed amber and
   never as done, because an inference is not evidence.
-- **Run Claude from the browser.** Spawn a session in a lane's directory, stream
-  its output, send follow-ups, resume any past session.
+- **Run Claude from the browser.** A real terminal (tmux + a real PTY,
+  rendered with xterm.js) attached to a lane's directory — the exact TUI you'd
+  see locally, fully interactive, resumable, and attachable from a real
+  terminal too via `ccam lanes shell`.
 - **Analytics, alerts, Kanban and a workflow view**, plus an MCP server and a CLI.
 
 ## Requirements