refactor: fail loud, tighten types, remove speculative abstraction

Fail loud at the boundary:
- substitute_template raises ConfigError on unresolved {{...}}; no more
  silent literal placeholders in download URLs.
- parse_profile raises ConfigError when 'os' is missing -- no
  raw.get("os", "linux") default that silently masks typos.
- urllib download failures wrapped to FlowError.
- bootstrap _execute_action dispatches phases explicitly and raises
  on unhandled phase; no more "anything else runs as shell".

Direct access over defensive wrapping:
- plan_bootstrap requires env; plan_install requires pm. Drop the
  dead `or os.environ` / `or detect_package_manager()` fallbacks.
- InstalledState.from_dict raises ConfigError on missing fields
  rather than .get(..., default).
- Replace `x or {}` chains with explicit `x if x is not None else {}`
  in package resolution; catalog validates type/platform-map/install
  shapes at parse.

One canonical form / direct access:
- Path.home() replaced with paths.HOME in services/packages.py and
  commands/completion.py. paths.HOME is the single source now.
- Use Path.is_relative_to for install-path containment instead of
  str.startswith.

Domain purity:
- domain/containers/resolution.resolve_mounts takes a filesystem_check
  predicate; service passes the probe in. Domain no longer touches
  the filesystem directly.

No speculative abstraction:
- Drop the `allow_sudo` field entirely. The _script_uses_sudo check
  it gated was bypassable (substring match) and gave false confidence;
  the manifest is fully user-trusted anyway.
- Delete dead terminfo_fix_command + RemoteService.fix_terminfo
  (no command surface exposes them).
- FileSystem.remove_tree no longer swallows errors via ignore_errors;
  callers opt into missing_ok if needed.

Typed enums:
- PackageDef.type, AppConfig.container_runtime as Literal[...].
  container_runtime values validated at config parse.

Completion bypasses runtime no longer:
- complete(ctx, ...) threads context; ContainerRuntime and state-file
  reads go through ctx.runtime instead of constructing primitives.

Tests added for: template raise, missing os raise, env/pm required,
unknown phase raise, no allow_sudo gate, URL download failure, install
path escape, corrupt installed.json, container_runtime Literal,
filesystem_check controls mounts.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

tests/test_domain_packages_planning.py

@@ -1,7 +1,11 @@
 """Tests for package install/remove planning."""
 
+import inspect
 from pathlib import Path
 
+import pytest
+
+from flow.core.errors import FlowError
 from flow.domain.packages.models import (
     InstalledPackage,
     InstalledState,
@@ -16,7 +20,7 @@ def _pkg(name, type="pkg", sources=None, source=None, version=None,
         name=name, type=type, sources=sources or {},
         source=source, version=version, asset_pattern=asset_pattern,
         platform_map=platform_map or {}, extract_dir=None, install={},
-        post_install=None, allow_sudo=False,
+        post_install=None,
     )
 
 
@@ -62,3 +66,15 @@ class TestPlanRemove:
     def test_remove_not_installed(self):
         plan = plan_remove(["missing"], InstalledState())
         assert len(plan.remove_ops) == 0
+
+
+class TestPlanInstallSignature:
+    def test_pm_is_required_positional(self):
+        sig = inspect.signature(plan_install)
+        param = sig.parameters["pm"]
+        assert param.default is inspect.Parameter.empty
+
+    def test_pkg_without_pm_raises(self):
+        pkgs = [_pkg("fd", sources={"apt": "fd-find"})]
+        with pytest.raises(FlowError, match="No supported package manager"):
+            plan_install(pkgs, InstalledState(), "linux-x64", None)