wip(k1): checkpoint connection recovery rewrite

Capture the current unreleased K1 connection, recovery, lifecycle, viewer, and test work as a single known-bad baseline for subsequent fixes.

src/k1link/viewer/rerun_bridge.py

@@ -1,5 +1,6 @@
 from __future__ import annotations
 
+import errno
 import logging
 import math
 import socket
@@ -86,8 +87,19 @@ def _select_available_grpc_port(
                 # Rerun binds all local interfaces. Probe the same address class
                 # so a previous recording retained by a late viewer is detected.
                 probe.bind(("0.0.0.0", candidate))
-            except OSError:
-                continue
+            except OSError as exc:
+                if exc.errno == errno.EADDRINUSE:
+                    continue
+                if exc.errno in {errno.EACCES, errno.EPERM}:
+                    raise PermissionError(
+                        exc.errno,
+                        "Permission denied while probing local Rerun gRPC "
+                        f"port {candidate}",
+                    ) from exc
+                raise RuntimeError(
+                    "Could not probe local Rerun gRPC "
+                    f"port {candidate}: {type(exc).__name__}: {exc}"
+                ) from exc
         return candidate
     raise RuntimeError(
         "No local Rerun gRPC port is available in "