Import mcp-to-cli from the rhema workspace

The crate maps MCP tool catalogs to clap commands and back, and has no
rhema dependencies — it was in-tree only because the workspace glob
reached it. Its own repository gives it its own release cadence and
its own crates.io token, scoped to this crate alone.

tests/common/mod.rs

@@ -0,0 +1,46 @@
+//! Shared helpers for the mapping matrix: argv driving and payload
+//! unwrapping.
+
+use mcp_to_cli::{Payload, ToolInfo, args};
+
+/// A [`ToolInfo`] from parts, for inline schemas.
+pub fn tool(name: &str, description: &str, input_schema: serde_json::Value) -> ToolInfo {
+    ToolInfo {
+        name: name.to_owned(),
+        description: description.to_owned(),
+        input_schema,
+    }
+}
+
+/// Parses `argv` (no program name) against `cmd`; `None` is clap
+/// rejecting the argv — the usage-error path.
+pub fn parse(cmd: &clap::Command, argv: &[&str]) -> Option<clap::ArgMatches> {
+    let mut full: Vec<String> = vec!["srv".to_owned()];
+    full.extend(argv.iter().map(|a| (*a).to_owned()));
+    cmd.clone().try_get_matches_from(full).ok()
+}
+
+/// Parses clap-valid `argv` and maps the matched tool.
+pub fn run(
+    cmd: &clap::Command,
+    argv: &[&str],
+) -> Result<mcp_to_cli::Payload, mcp_to_cli::MappingError> {
+    let matches = parse(cmd, argv).expect("argv parses");
+    args(cmd, &matches)
+}
+
+/// The mapped object of a payload that must be mapped.
+pub fn mapped(payload: Payload) -> serde_json::Value {
+    match payload {
+        Payload::Mapped(value) => value,
+        other => panic!("expected a mapped payload, got {other:?}"),
+    }
+}
+
+/// The raw string of a payload that must be the `--json` override.
+pub fn overridden(payload: Payload) -> String {
+    match payload {
+        Payload::Overridden(raw) => raw,
+        other => panic!("expected an overridden payload, got {other:?}"),
+    }
+}