docs(readme): name the okf 1.1 server by full path -- a bare okf finds the 0.8.5 dependency

The example config now has the placeholder `/path/to/okf` for `command`, and the README explains
how to find the real path (`command -v okf` outside this project's environment). It also explains
why the bare name fails under `uv run`: it resolves to this framework's own okf 0.8.5, which has
no `mcp` command. A new pin asserts that the example's command is an absolute path; it was red at
daccdbe. The xfail smoke test stays as the measurement behind the rule.

Chose this over lifting the okf dependency to 1.1: it fixes the startup failure without a version
bump and without touching --prepass-payload.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>

examples/okf-server.mcp.json

@@ -3,7 +3,7 @@
     {
       "name": "okf",
       "transport": "stdio",
-      "command": "okf",
+      "command": "/path/to/okf",
       "args": ["mcp", "--root", "/path/to/folder/with/your/knowledge-bases"],
       "allowed_tools": ["okf_list", "okf_describe", "okf_ask", "okf_fetch"],
       "timeout_seconds": 120