sl0ptty: M7 — layout files and suspended panes

A session can be a file:

  layout {
      tab name="api" purpose="project:api.a1b2c3" cwd="~/dev/api" {
          pane purpose="agent:main" command="pi"
          pane split="rows" {
              pane purpose="service:web" command="npm run dev" suspended=true
              pane purpose="shell:scratch"
          }
      }
  }

built by --layout at startup or applied to a running session with
{"cmd":"apply-layout", path|kdl, replace?}. Idempotency stays with the caller,
which is where sl0ppi's CLI design already puts it: diff list-tabs against the
projects on disk, then apply what is missing. close-tab completes that loop.

Purposes a layout declares are locked, so identity comes from the file rather
than from whatever the program inside prints — tested by having a pane try to
take one in-band and be refused.

Suspended panes: a pane that exists, is laid out, and has run nothing, showing
what it would run and starting on its first keystroke (which is consumed, not
forwarded). This is sl0ppi's D6 — a root with twelve projects must not become
twelve running servers — and it is the reason  can be cheap.

Also fixes a test-isolation bug latent since M2: the live tests attached to the
session called "main", which is whatever happens to exist on the box rather
than one they created. They now use a unique session per run, which is how a
run that had somebody else's htop in it became reproducible.

284 checks green (257 headless + 27 live).

1 files changed, 8 insertions, 2 deletions

diff --git a/tests/live_m0.py b/tests/live_m0.py
index 58720c2..ead8092 100644
--- a/tests/live_m0.py
+++ b/tests/live_m0.py
@@ -4,16 +4,22 @@
 The headless dump proves composition; this proves the parts headless cannot:
 raw mode, the diff emitter, SIGWINCH, and the quit path.
 """
-import os, pty, re, select, signal, struct, subprocess, sys, termios, time, fcntl
+import os, pty, uuid, re, select, signal, struct, subprocess, sys, termios, time, fcntl
 
 BIN = os.path.join(os.path.dirname(__file__), "..", "build", "sl0ptty")
 
 
+# A unique session per run. Without this the tests attach to whatever "main"
+# happens to exist on the box, which is somebody else's terminal.
+SESSION = "test-" + uuid.uuid4().hex[:8]
+
+
 def spawn(cols=60, rows=12, argv=None):
     pid, fd = pty.fork()
     if pid == 0:
         os.environ["TERM"] = "xterm-ghostty"
-        os.execv(BIN, [BIN] + (argv or ["--", "/bin/sh", "-i"]))
+        os.environ["SL0PTTY_CONFIG"] = "/nonexistent/sl0ptty.kdl"
+        os.execv(BIN, [BIN, "-s", SESSION] + (argv or ["--", "/bin/sh", "-i"]))
         os._exit(127)
     fcntl.ioctl(fd, termios.TIOCSWINSZ, struct.pack("HHHH", rows, cols, 0, 0))
     return pid, fd