fix(terminal): merge-time fixes for the silent-failure paths (#431)

- While another device holds the pane width (_paneWidthRefused), a resize
  now asks for the container's width without applying it locally
  (_geometryForResizeRequest: rows follow the container, columns stay at
  the PTY's). Fitting first re-wrapped the whole buffer to the container
  and back on every 30s mobile retry, and throttledResize ran the
  scrollback clear for a resize that brings no redraw. selectSession
  clears the flag, since it belongs to the previous pane. New unit tests
  run the real mixin against a fake terminal and fail without the fix.
- Session seeds _ptyCols/_ptyRows at spawn (_notePtySpawnGeometry), so a
  reattached pane reports its tmux window's real size through ptyGeometry.
- Session.resize's declined-branch comment names ptyGeometry, not the
  deleted ptyCols/ptyRows getters.
- Delete the dead terminalGeometryAgrees() and its window export.
- test/xterm-private-api.test.ts header: it pins the exact locked version,
  so any bump fails, not only a major.
- The main-terminal fit sweep also matches fitAddon?.fit?.(), and
  CLAUDE.md names the modules it actually covers.

Co-Authored-By: Claude Opus 5.5 (1M context) <noreply@anthropic.com>

src/web/public/app.js

@@ -6652,6 +6652,10 @@ class CodemanApp {
       // Fit terminal to container BEFORE writing any buffer data.
       // If the browser was resized while viewing another session, the terminal
       // canvas may be at stale dimensions — content would render at wrong width.
+      // A width refusal belonged to the PREVIOUS session's pane, and while it
+      // stands sendResize keeps the columns it last adopted; this pane's own
+      // report re-establishes it if another device holds this one too.
+      this._paneWidthRefused = false;
       this.syncTerminalGeometry();
 
       // Also push the new dimensions to the PTY. Without this, codex/codeman