feat(lanes): prime and nudge codex lanes into declaring their own stage

A codex lane's declared stage has always depended entirely on the session
reading AGENTS.md and calling `ccam stage` on its own — no hook, no wrapper,
no enforcement. Two additions make that more reliable without touching the
declared-wins / inferred-never-done invariants:

- LaneConsolePane pre-fills a codex pane's opening prompt with a plain-text
  stage-declaration checklist built from the lane's own pipeline_nodes —
  the same up-front priming a Claude lane gets from its pre-filled
  /ccam:ship-feature-lane skill command, just as prose since Codex has no
  slash commands.
- server/lib/codex-nudge.js sweeps every 60s and types a one-line reminder
  into a lane's live tmux pane (tmux.sendText, a new literal-text primitive
  alongside sendCommand) when its fresh detected_stage has sat undeclared
  for over two minutes. It never writes stage/detected_stage itself — any
  resulting declaration is still the codex session's own real ccam stage
  call, just server-prompted instead of relying on memory alone.

server 1354/1354, client 449/449, tsc clean.

server/__tests__/tmux.test.js

@@ -50,6 +50,23 @@ describe("tmux wrapper", () => {
     assert.deepEqual(calls[1], ["set-option", "-t", "ccam-lane-1", "mouse", "on"]);
   });
 
+  it("sendText types the literal string and presses Enter, with no quoting", () => {
+    const calls = [];
+    tmux.__setExecImpl((args) => {
+      calls.push(args);
+      return "";
+    });
+    tmux.sendText("ccam-lane-1", 'Reminder: run "ccam stage implement"');
+    assert.deepEqual(calls[0], [
+      "send-keys",
+      "-t",
+      "ccam-lane-1",
+      "-l",
+      'Reminder: run "ccam stage implement"',
+    ]);
+    assert.deepEqual(calls[1], ["send-keys", "-t", "ccam-lane-1", "Enter"]);
+  });
+
   it("killSession never throws when the session is already gone", () => {
     tmux.__setExecImpl(() => {
       const e = new Error("no such session");