fix(dashboard): hoist claude_argv to Bottle ABC so smolmachines pane attach works

Launching a smolmachines agent from the dashboard inside tmux
crashed with

  AttributeError: 'SmolmachinesBottle' object has no attribute
  'claude_docker_argv'

because the tmux pane-respawn path called
`bottle.claude_docker_argv(...)` directly — a method that only
existed on DockerBottle. The foreground-handoff path (curses
endwin → subprocess.run → restore) doesn't hit it; it goes
through `bottle.exec_claude` which is on the ABC.

- Move the argv builder onto the `Bottle` ABC as
  `claude_argv(argv, *, tty=True) -> list[str]`. Both backends
  implement it; both `exec_claude` impls collapse to
  `subprocess.run(self.claude_argv(argv, tty=tty), check=False)`.

- DockerBottle: rename `claude_docker_argv` → `claude_argv`,
  body unchanged.

- SmolmachinesBottle: extract the argv-building from
  `exec_claude` into `claude_argv`; the new method returns the
  full `smolvm machine exec --name … -- runuser -u node --
  claude …` argv. The `runuser` switch lives on the
  exec-framing prefix so the dashboard's
  `_build_resume_argv_with_fallback` split-at-"claude" trick
  keeps the UID switch when wrapping the claude tail in
  `sh -c "… --continue || …"`.

- Dashboard: drop the docker-specific wording — local + helper
  arg names `docker_argv` → `claude_argv`; docstrings on
  `_build_resume_argv_with_fallback`, `_build_split_pane_argv`,
  `_build_respawn_pane_argv` now say "backend-exec argv". The
  shell-fallback wrap is unchanged; the existing logic works
  for smolmachines because `claude` is still the marker token.

Tests:
- `tests/unit/test_smolmachines_bottle.py` (new): locks down
  the smolmachines argv shape — prompt-file flag injection,
  guest-env `-e K=V` forwarding, TTY toggle, runuser-precedes-
  claude invariant.
- `test_docker_bottle.py`: TestClaudeDockerArgv →
  TestClaudeArgv; method renames follow.
- `test_dashboard_active_agents.py`: docstring follow.

615 unit tests pass.

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>

claude_bottle/backend/smolmachines/bottle.py

@@ -75,6 +75,21 @@ class SmolmachinesBottle(Bottle):
         # because exec doesn't inherit from machine_create's env.
         self._guest_env = dict(guest_env or {})
 
+    def claude_argv(
+        self, argv: list[str], *, tty: bool = True,
+    ) -> list[str]:
+        flags = ["smolvm", "machine", "exec", "--name", self.name]
+        if tty:
+            flags += ["-i", "-t"]
+        flags += _env_flags_for("node")
+        flags += _guest_env_flags(self._guest_env)
+        claude_tail = ["claude"]
+        if self._prompt_path:
+            claude_tail += ["--append-system-prompt-file", self._prompt_path]
+        claude_tail += argv
+        flags += ["--", "runuser", "-u", "node", "--", *claude_tail]
+        return flags
+
     def exec_claude(self, argv: list[str], *, tty: bool = True) -> int:
         """Run `claude` interactively inside the VM as the `node`
         user. Inherits the operator's terminal (stdin / stdout /
@@ -89,18 +104,9 @@ class SmolmachinesBottle(Bottle):
         UID switches via `runuser -u node --` (not `-l`) so we
         avoid login-shell wiring. HOME / USER come from `smolvm
         -e` instead, which sets them on the process env."""
-        flags = ["smolvm", "machine", "exec", "--name", self.name]
-        if tty:
-            flags += ["-i", "-t"]
-        flags += _env_flags_for("node")
-        flags += _guest_env_flags(self._guest_env)
-        claude_argv = ["claude"]
-        if self._prompt_path:
-            claude_argv += ["--append-system-prompt-file", self._prompt_path]
-        claude_argv += argv
-        flags += ["--", "runuser", "-u", "node", "--", *claude_argv]
-        result = subprocess.run(flags, check=False)
-        return result.returncode
+        return subprocess.run(
+            self.claude_argv(argv, tty=tty), check=False,
+        ).returncode
 
     def exec(self, script: str, *, user: str = "node") -> ExecResult:
         """Run a POSIX shell script as `user` (default `node`) and