test: add a duplicate-tool-names test server for the #1957 repro

Nothing in the repo could serve the shape this fix is about: every preset
registers a unique name, and the SDK's `registerTool` rejects a repeat. So the
only reproduction was a unit test — there was no way to smoke the real app
against a server that returns duplicates.

Adds `ServerConfig.duplicateToolNames` (a list of registered tool names) to the
composable test server, plumbed through the JSON config, and a showcase config
`duplicate-tool-names-http.json`. The named tools are emitted a second time in
`tools/list` with the same `name` and a "(duplicate)" title.

The repeats are appended after the whole list rather than placed beside their
twin. That is both the realistic shape (two tool sources concatenated) and what
makes the defect observable: React matches a leading run of same-key children
first, so a head-adjacent duplicate happens to line up and the bug hides. Only
a separated pair collides in the keyed map and orphans a row — verified both
ways against the prod bundle.

The `tools/list` override is shared with the existing pagination handler (which
already hand-builds the list); with no `maxPageSize` it returns a single
unbounded page. Duplication happens before pagination, so a duplicated pair can
straddle a page boundary the way a real server's would.

Also adds a ToolControls test for this appended ordering, distinct from the
reporter's interleaved fixture, and documents the config in the README showcase
table.

Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01SW1p8E2uiyyLx4RKwrwSrt

test-servers/configs/duplicate-tool-names-http.json

@@ -0,0 +1,17 @@
+{
+  "serverInfo": {
+    "name": "duplicate-tool-names",
+    "version": "1.0.0"
+  },
+  "tools": [
+    { "preset": "get_weather" },
+    { "preset": "get_temp" },
+    { "preset": "echo" },
+    { "preset": "add" }
+  ],
+  "duplicateToolNames": ["get_weather", "echo"],
+  "transport": {
+    "type": "streamable-http",
+    "port": 3142
+  }
+}