fix(run): keep the tmux pane exactly as wide as xterm

Scrolling a lane console repainted history with stray characters glued to
the left edge of blank lines. Reproduced against a real tmux attach: a pane
WIDER than xterm makes every over-long row autowrap its tail onto the next
row's left margin, and tmux — believing that row unchanged — never repaints
over it. One column of difference leaves one stray character per wrapped
line, two columns leave two; matched widths render clean.

TerminalView only reported its size on WS open and on the container's
ResizeObserver, so nothing corrected:
- cols moving with no container resize (webfont load, page zoom, scrollbar)
- tmux's `window-size latest` letting a second attach client (another tab,
  `ccam lanes shell`) resize the window out from under this one

Size is now reported from xterm's own onResize, re-asserted when the
terminal regains focus, and never reported as zero — the console collapses
with CSS, and fitting a 0x0 container would resize the real pane to nothing.

client 447/447, tsc clean.

docs/API.md

@@ -1809,7 +1809,7 @@ Sent when a notification is created.
 
 #### /ws-pty/:runId — PTY frames
 
-A dedicated binary WebSocket stream (not JSON-framed) for tmux-backed PTY transport. Established by the Workspace TerminalView component on lane load; endpoint is `/ws-pty/:runId` where `runId` comes from `POST /api/run`. Frames are raw PTY output (stdin echoes, command output, prompt updates, terminal control sequences) as binary blobs; the client feeds each frame to xterm.js for live rendering. The same tmux session can have multiple simultaneous clients (browser Workspace, `ccam lanes shell`, other tools), all receiving the same frames live-synced. Resize events: the client sends a `TIOCSWINSZ` ioctl down the pane's pty when the browser terminal is resized, so window-sensitive commands (e.g. pagers, text editors) adapt to the viewport size. The WebSocket connection inherits the same loopback same-origin guard and optional token auth as other `/api/*` routes. The client re-attaches automatically 1.5 s after an unexpected close (server restart, network blip) — tmux keeps the session alive, so the re-attach repaints the pane in full. It stops retrying only after the server's one-shot `{"type":"exit"}` frame, which means the pane process itself ended. Without that retry a dropped socket left the pane frozen on its last painted frame: it still looked live, but no keystroke and no mouse report (wheel scroll included) reached tmux again.
+A dedicated binary WebSocket stream (not JSON-framed) for tmux-backed PTY transport. Established by the Workspace TerminalView component on lane load; endpoint is `/ws-pty/:runId` where `runId` comes from `POST /api/run`. Frames are raw PTY output (stdin echoes, command output, prompt updates, terminal control sequences) as binary blobs; the client feeds each frame to xterm.js for live rendering. The same tmux session can have multiple simultaneous clients (browser Workspace, `ccam lanes shell`, other tools), all receiving the same frames live-synced. Resize events: the client sends a `{"type":"resize","cols","rows"}` text frame and the server applies it as a `TIOCSWINSZ` ioctl down the pane's pty, so window-sensitive commands (e.g. pagers, text editors) adapt to the viewport size. The client reports its size from **xterm's own `onResize`**, not from the container's `ResizeObserver` — cols also move when the webfont finishes loading or the page zooms, neither of which resizes the observed element — and re-asserts it whenever the terminal regains focus, because `window-size latest` lets a second attach client (another tab, `ccam lanes shell`) resize the tmux window out from under this one. Keeping the two widths equal is not cosmetic: a tmux pane **wider** than xterm makes every over-long row autowrap its tail onto the next row's left margin, and tmux never repaints a row it believes unchanged — so stray characters stay glued to the left edge of blank lines, visible as soon as a scroll repaints history. A zero size (the console collapses with CSS, leaving the container 0×0) is never reported. The WebSocket connection inherits the same loopback same-origin guard and optional token auth as other `/api/*` routes. The client re-attaches automatically 1.5 s after an unexpected close (server restart, network blip) — tmux keeps the session alive, so the re-attach repaints the pane in full. It stops retrying only after the server's one-shot `{"type":"exit"}` frame, which means the pane process itself ended. Without that retry a dropped socket left the pane frozen on its last painted frame: it still looked live, but no keystroke and no mouse report (wheel scroll included) reached tmux again.
 
 #### cc_config_changed