ui: Constants refactor (#26908)

* refactor: Constants

* refactor: Constants/Enums cleanup

* refactor: Constant objects instead of multiple single value constants

* refactor: Cleanup constants

tools/ui/src/lib/constants/headers.constants.ts

@@ -0,0 +1,35 @@
+/** HTTP header handling for API and MCP requests. */
+export const HEADERS = {
+	/** Canonical casing for the Authorization header (RFC 7235) */
+	AUTHORIZATION: 'Authorization',
+	/** Bearer scheme prefix used for Authorization headers (RFC 6750) */
+	BEARER: 'Bearer ',
+	/** Content-Type HTTP header name */
+	CONTENT_TYPE: 'Content-Type',
+	/** Partial-redaction rules for MCP headers: header name -> visible trailing chars */
+	PARTIAL_REDACT: new Map<string, number>([['mcp-session-id', 5]]),
+
+	/** Header names whose values should be redacted in diagnostic logs */
+	REDACTED: new Set([
+		'authorization',
+		'api-key',
+		'cookie',
+		'mcp-session-id',
+		'proxy-authorization',
+		'set-cookie',
+		'x-auth-token',
+		'x-api-key'
+	]),
+
+	/** Header carrying the stream-session identity (conversation id, optionally with a model suffix) */
+	X_CONVERSATION_ID_HEADER: 'X-Conversation-Id',
+
+	/** Header asking the server to encode a tool's output differently, e.g. read_file returning base64. */
+	X_RESP_TYPE_HEADER: 'x-resp-type',
+
+	/** Header carrying the working directory a tool call runs in; the model cannot override it */
+	X_TOOL_CWD_HEADER: 'x-tool-cwd'
+};
+
+/** `X_RESP_TYPE_HEADER` value that makes read_file return raw bytes as base64 instead of text. */
+export const RESP_TYPE_BASE64 = 'base64';