test: drop strictPort and document the port collision instead

strictPort was a new test-server config option — plus its validation and 18
tests — invented solely to keep one fixture's hard-coded issuer port honest.
That is infrastructure built for a screenshot, so it goes.

test-servers/src is now byte-identical to v2/main again. The fixture keeps its
fixed port and docs/test-servers.md carries the caveat instead, written to be
actionable rather than merely cautionary: the failure mode is confusing rather
than obvious, since a relocated server leaves discovery pointing at whatever
unrelated process holds 8091, so the note says to check the port before
believing what the flow does.

Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_018MvNbmAtQuWhDvzi4yXDju
Signed-off-by: cliffhall <cliff@futurescale.com>

test-servers/configs/oauth-insecure-token-endpoint-http.json

@@ -21,7 +21,6 @@
   },
   "transport": {
     "type": "streamable-http",
-    "port": 8091,
-    "strictPort": true
+    "port": 8091
   }
 }