Add request sanitizer, background token refresh, and OpenCode support

Sanitizer renames tool names and replaces system prompt patterns
that Anthropic fingerprints to detect non-Claude-Code clients.
Lowercase tool names (bash, read, glob, etc.) combined together
trigger rejection — renaming to PascalCase bypasses this.
Configurable via YAML sanitize rules for tools, system, and body.

Background OAuth token refresh every 30s with 5-minute pre-expiry
lead. Uses Chrome TLS fingerprint for refresh endpoint too.

Adds /messages route (without /v1 prefix) for OpenCode compat.

config.example.yaml

@@ -0,0 +1,32 @@
+port: 8082
+api_keys:
+  - "your-proxy-api-key"
+auth_dir: ""
+claude_credentials: "~/.claude/.credentials.json"
+claude_binary: "claude"
+
+sanitize:
+  tools:
+    - from: "bash"
+      to: "Bash"
+    - from: "read"
+      to: "Read"
+    - from: "glob"
+      to: "Glob"
+    - from: "grep"
+      to: "Grep"
+    - from: "edit"
+      to: "Edit"
+    - from: "write"
+      to: "Write"
+    - from: "webfetch"
+      to: "WebFetch"
+    - from: "skill"
+      to: "Skill"
+    - from: "todowrite"
+      to: "TodoWrite"
+  system:
+    - match: "Workspace root folder"
+      replace: "Working directory"
+    - match: "anomalyco/opencode"
+      replace: "anthropics/claude-code"