Fix Reckless search command not finding partial matches

The Reckless search command was only returning a result if you
searched a perfect match, which is not too helpful.  This updates the
command so that partial search matches return a result.

Before:
reckless search bolt
Search exhausted all sources
reckless search bol
Search exhausted all sources
reckless search bolt12-pris
Search exhausted all sources

After:
reckless search bolt
Plugins matching 'bolt':
  bolt12-prism (https://github.com/lightningd/plugins)
reckless search bol
Plugins matching 'bol':
  bolt12-prism (https://github.com/lightningd/plugins)
reckless search bolt12-pris
Plugins matching 'bolt12-pris':
  bolt12-prism (https://github.com/lightningd/plugins)

Changelog-Fixed: reckless search now returns partial matches instead of requiring exact plugin names.

tests/test_reckless.py

@@ -224,6 +224,32 @@ def test_search(node_factory):
     assert r.search_stdout('found testplugpass in source: https://github.com/lightningd/plugins')
 
 
+def test_search_partial_match(node_factory):
+    """test that partial/substring search returns multiple matches"""
+    n = get_reckless_node(node_factory)
+
+    # Search for partial name "testplug" - should find all test plugins
+    r = reckless([f"--network={NETWORK}", "search", "testplug"], dir=n.lightning_dir)
+    # Should show the "Plugins matching" header
+    assert r.search_stdout("Plugins matching 'testplug':")
+    # Should list multiple plugins (all start with "testplug")
+    assert r.search_stdout('testplugpass')
+    assert r.search_stdout('testplugfail')
+    assert r.search_stdout('testplugpyproj')
+    assert r.search_stdout('testpluguv')
+
+    # Search for "pass" - should find testplugpass
+    r = reckless([f"--network={NETWORK}", "search", "pass"], dir=n.lightning_dir)
+    assert r.search_stdout("Plugins matching 'pass':")
+    assert r.search_stdout('testplugpass')
+    # Should not find plugins without "pass" in name
+    assert not r.search_stdout('testplugfail')
+
+    # Search for something that doesn't exist
+    r = reckless([f"--network={NETWORK}", "search", "nonexistent"], dir=n.lightning_dir)
+    assert r.search_stdout("Search exhausted all sources")
+
+
 def test_install(node_factory):
     """test search, git clone, and installation to folder."""
     n = get_reckless_node(node_factory)