fix: effort-proxy mapping max→xhigh for GPT, add EFFORT_MAPPING.md

- Fix effort-proxy direction: GPT-5.5 natively supports xhigh but not max,
  so map max→xhigh (was incorrectly xhigh→max)
- Add EFFORT_MAPPING.md with full mapping table for all providers:
  Anthropic, GPT-5.5, DeepSeek V4, Kimi K2.6, Gemini 3.x
- Update proxy docstring and comments

claude_setup.sh

@@ -105,11 +105,16 @@ else
   install_proxy
 fi
 
-# ── 4b. effort-proxy wrapper (патч xhigh->max для claude-code-proxy) ─────────
+# ── 4b. effort-proxy wrapper (маппинг effort для GPT: max->xhigh) ─────────
 EFFORT_PROXY_BIN="$BIN_DIR/claude-gpt-effort-proxy.py"
 cat > "$EFFORT_PROXY_BIN" << 'PYEOF'
 #!/usr/bin/env python3
-"""Reverse proxy: rewrites "xhigh" effort -> "max" for claude-code-proxy (bug in <=0.0.13)."""
+"""Effort mapping proxy for GPT backend.
+
+GPT-5.5 natively supports: low, medium, high, xhigh (no "max").
+Claude Code may send "max" effort — we map it to "xhigh" (highest GPT level).
+See EFFORT_MAPPING.md for the full mapping table across all providers.
+"""
 import http.client, http.server, sys
 
 UPSTREAM_PORT = int(sys.argv[1]) if len(sys.argv) > 1 else 18766
@@ -120,7 +125,7 @@ class _Proxy(http.server.BaseHTTPRequestHandler):
         body = b""
         if cl := self.headers.get("Content-Length"):
             body = self.rfile.read(int(cl))
-        body = body.replace(b'"xhigh"', b'"max"')
+        body = body.replace(b'"max"', b'"xhigh"')
         try:
             conn = http.client.HTTPConnection("localhost", UPSTREAM_PORT, timeout=300)
             hdrs = dict(self.headers)