Plane client, transports and executor adapters

Plane: paginated issue/comment/state/label/member access, one client per
terminal identity. Transports: local (setsid-detached runner) and warpgate-ssh
(win10-ps.sh / win10-put.sh relay, schtasks launch, taskkill on timeout).
Executors share a runner shape (prompt.md, exit.txt marker) with codex,
claude-code and shell adapters for last message and thread id.

agentd/transports/__init__.py

@@ -0,0 +1,24 @@
+"""Transports: how agentd reaches a terminal's machine (files, detached launch, kill).
+
+Interface (duck-typed, see docs/executor-contract.md):
+  os, join(*parts), quote(s), default_run_root()
+  mkdir(path, clean=False), write_text(path, text), read_text(path) -> str|None,
+  grep_first(path, needle) -> str|None, tail(path, n) -> str
+  runner(run_dir, cwd, command, stdout_name) -> (script_name, script_text)
+  launch(task, script_path, run_dir), kill(task, run_dir), forget(task)
+  process_count(name) -> int|None (None = unreachable)"""
+
+
+class TransportError(Exception):
+    pass
+
+
+def make_transport(cfg, terminal):
+    kind = cfg.terminals[terminal]["transport"]
+    if kind == "local":
+        from .local import LocalTransport
+        return LocalTransport(cfg, terminal)
+    if kind == "warpgate-ssh":
+        from .warpgate_ssh import WarpgateSshTransport
+        return WarpgateSshTransport(cfg, terminal)
+    raise TransportError("unknown transport %s" % kind)