fix(hashline): replaced delimiter heuristics with tree-sitter validation

- Replaced heuristic delimiter-balance boundary repairs with tree-sitter guided variants.
- Added combinatorial search over replacement boundary keep/drop variants and syntax-essential row validation.
- Removed obsolete `CloserSpareAmbiguityError` along with custom JSX parsing and delimiter counting helpers.
- Updated warning and error messages to include unified boundary diagnostics.

packages/coding-agent/test/tools/lsp-regressions.test.ts

@@ -2645,7 +2645,7 @@ describe("lsp regressions", () => {
 				rootMarkers: [],
 				isLinter: true,
 			};
-			const server = installFakeLsp((message, srv) => {
+			installFakeLsp((message, srv) => {
 				if (message.method === "initialize") {
 					srv.send({
 						jsonrpc: "2.0",