Add Python example for create_with_server_id fix (#9)

Land examples/api/create_by_server_id.py, third of the seven
create_by_* examples and the first of the four routing variants
added in gopher-orch 0.1.23. Direct port of
gopher-mcp-js/examples/api/create_by_server_id.ts, which itself
ports gopher-orch/examples/sdk/api/create_by_server_id.cc.

Behaviour:

- Scopes the agent to a single MCP server in the caller's workspace
  by id. Internally hits the same GET /v1/mcp-servers endpoint as
  create_with_api_key under the Bearer api key, but adds the
  "?serverId={id}" routing query so the response carries only the
  matching server entry. Use this when the api key owns several
  MCP servers but the agent should bind to exactly one.

- Provider defaults to AnthropicProvider; the model comes from the
  LLM_MODEL env var. Refuses to call the FFI when any of the three
  required env vars (LLM_MODEL, GOPHER_API_KEY, GOPHER_MCP_SERVER_ID)
  is still the placeholder, printing a clear error to stderr and
  exiting 1.

- Reads the routing parameter from GOPHER_MCP_SERVER_ID,
  matching the JS sibling's env-var name so a downstream user can
  share env across the JS and Python toolchains. Same pattern for
  the next three routing variants (server_name, gateway_id,
  gateway_name).

- Accepts queries as positional argv with the canned "What time is
  it in Tokyo?" fallback. try / finally with agent.dispose() so the
  native handle is always released.

Requires the create_with_server_id factory landed earlier in this
PR series; against the vendored 0.1.1 dylib the example exits with
an AgentError from the null-handle pump because the C symbol is
missing. Against a fresh gopher-orch 0.1.23 build the example
completes end-to-end.

Verified locally: placeholder refusal path exits 1 with a clear
diagnostic; syntax check clean; no forbidden tokens.

Author: RahulHere

examples/api/create_by_server_id.py

@@ -0,0 +1,116 @@
+#!/usr/bin/env python3
+"""
+SDK example for GopherAgent.create_with_server_id.
+
+Python port of gopher-mcp-js/examples/api/create_by_server_id.ts, which
+itself ports gopher-orch/examples/sdk/api/create_by_server_id.cc.
+
+Scopes a GopherAgent to a single MCP server in the caller's workspace
+by id. Internally this hits the same GET /v1/mcp-servers endpoint as
+create_with_api_key under the Bearer api key, but adds the
+"?serverId={id}" routing query so the response carries only the
+matching server entry. Use this when the api key owns several MCP
+servers but the agent should bind to exactly one.
+
+Provider defaults to AnthropicProvider; the model is taken from
+LLM_MODEL. Override either via env or by editing the constants in
+main().
+
+Configuration (env vars):
+    GOPHER_API_KEY        Gopher API key for /v1/mcp-servers
+    GOPHER_MCP_SERVER_ID  MCP server id to scope the agent to
+    LLM_PROVIDER          Optional. Defaults to "AnthropicProvider".
+    LLM_MODEL             Required. Model identifier the provider accepts.
+    DEBUG                 When set, ctypes prints library-resolution diagnostics.
+
+Usage:
+    python3 create_by_server_id.py                              # built-in query
+    python3 create_by_server_id.py "query one" "query two" ...  # supplied queries
+"""
+
+import os
+import sys
+import traceback
+
+from gopher_mcp_python import GopherAgent
+
+API_KEY_PLACEHOLDER = "{YOUR_GOPHER_API_KEY}"
+SERVER_ID_PLACEHOLDER = "{YOUR_MCP_SERVER_ID}"
+MODEL_PLACEHOLDER = "{YOUR_LLM_MODEL}"
+
+
+def env_or(name: str, fallback: str) -> str:
+    """Return os.environ[name] if non-empty, otherwise fallback."""
+    value = os.environ.get(name, "")
+    return value if value else fallback
+
+
+def main() -> None:
+    print("=== GopherAgent.create_with_server_id example ===")
+    print(f"Usage: python3 {sys.argv[0]} [query1] [query2] ...")
+    print(
+        "Env:   GOPHER_API_KEY GOPHER_MCP_SERVER_ID LLM_PROVIDER LLM_MODEL DEBUG"
+    )
+    print("")
+
+    queries = sys.argv[1:] if len(sys.argv) > 1 else ["What time is it in Tokyo?"]
+
+    provider = env_or("LLM_PROVIDER", "AnthropicProvider")
+    model = env_or("LLM_MODEL", MODEL_PLACEHOLDER)
+    api_key = env_or("GOPHER_API_KEY", API_KEY_PLACEHOLDER)
+    server_id = env_or("GOPHER_MCP_SERVER_ID", SERVER_ID_PLACEHOLDER)
+
+    print(f"Provider:      {provider}")
+    model_label = (
+        f"{model}  (set LLM_MODEL)" if model == MODEL_PLACEHOLDER else model
+    )
+    print(f"Model:         {model_label}")
+    api_key_label = (
+        f"{api_key}  (set GOPHER_API_KEY)"
+        if api_key == API_KEY_PLACEHOLDER
+        else "<set via GOPHER_API_KEY>"
+    )
+    print(f"API key:       {api_key_label}")
+    server_id_label = (
+        f"{server_id}  (set GOPHER_MCP_SERVER_ID)"
+        if server_id == SERVER_ID_PLACEHOLDER
+        else server_id
+    )
+    print(f"MCP server id: {server_id_label}")
+    print(f"Queries:       {len(queries)}")
+
+    if (
+        model == MODEL_PLACEHOLDER
+        or api_key == API_KEY_PLACEHOLDER
+        or server_id == SERVER_ID_PLACEHOLDER
+    ):
+        print(
+            "\nError: LLM_MODEL, GOPHER_API_KEY, and GOPHER_MCP_SERVER_ID "
+            "must all be set.",
+            file=sys.stderr,
+        )
+        sys.exit(1)
+
+    print("\nCreating agent via GopherAgent.create_with_server_id...")
+    agent = GopherAgent.create_with_server_id(provider, model, api_key, server_id)
+    print("Agent created successfully!")
+
+    try:
+        for i, query in enumerate(queries):
+            print(f"\nQuery {i + 1}: {query}")
+            answer = agent.run(query)
+            print(f"\nAgent Response {i + 1}:")
+            print("--------------------------------")
+            print(answer)
+            print("--------------------------------")
+    finally:
+        agent.dispose()
+
+
+if __name__ == "__main__":
+    try:
+        main()
+    except Exception as e:
+        print(f"Error: {e}", file=sys.stderr)
+        traceback.print_exc(file=sys.stderr)
+        sys.exit(1)