fix(mcp): accept --X as NAME positional, forward as install-context error

Python Click ignore_unknown_options=True assigns option-like args (--X)
to the NAME positional parameter, then mcp_install forwards them to
`apm install` which rejects them as unknown options. The Go impl was
incorrectly filtering --X out of NAME collection, producing a
'Missing argument NAME' error (mcp install context) instead of
'No such option: --X' (apm install context).

Fix: remove the startsWith(a, "-") guard so --X args ARE assigned to
NAME (matching Python's ignore_unknown_options behavior). When NAME
starts with '-', output the install-context error matching Python's
forwarding chain output.

Resolves PYTHON_CLI_CONTRACT_STATUS=1 in Python-vs-Go Parity Gate.

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

Author: github-actions[bot]

cmd/apm/cmd_mcp.go

@@ -94,9 +94,10 @@ func runMCPInstall(args []string) int {
 		case "--limit":
 			i++ // skip value
 		default:
-			// Python Click ignore_unknown_options=True puts --X args into ctx.args,
-			// not into the NAME positional. Only non-dash args are positional.
-			if !startsWith(a, "--limit=") && !startsWith(a, "-") && name == "" {
+			// Python Click ignore_unknown_options=True assigns --X args to the
+			// NAME positional (they do NOT go to ctx.args). Accept all
+			// unrecognized args (including --X) as NAME to match that behavior.
+			if !startsWith(a, "--limit=") && name == "" {
 				name = a
 			}
 		}
@@ -108,6 +109,15 @@ func runMCPInstall(args []string) int {
 		fmt.Fprintln(os.Stderr, "Error: Missing argument 'NAME'.")
 		return 2
 	}
+	// Python's mcp_install forwards NAME to `apm install --mcp NAME`, which
+	// rejects any option-like value as an unknown option. Mirror that error.
+	if startsWith(name, "-") {
+		fmt.Fprintln(os.Stderr, "Usage: apm install [OPTIONS] [PACKAGES]...")
+		fmt.Fprintln(os.Stderr, "Try 'apm install --help' for help.")
+		fmt.Fprintln(os.Stderr, "")
+		fmt.Fprintf(os.Stderr, "Error: No such option: %s\n", name)
+		return 2
+	}
 
 	cwd, _ := os.Getwd()
 	ymlPath, err := findApmYML(cwd)