add workspace grep engine + search.grep/cancel, editor.open --line

The pure-Dart content-search engine behind find-in-files (D-79): walks
the ignore-pruned workspace, fans files across worker isolates
(Isolate.run) for parallelism, matches each line with a literal
indexOf fast-path or a RegExp, and streams match batches with
cooperative cancellation. No ripgrep dependency; the search.grep IPC
contract is engine-agnostic so an rg accelerator can slot in later.

search.grep returns a searchId and streams search.match / search.done
(or search.error) events, mirroring files.watch; search.cancel stops
an in-flight search. The service reuses the files service's resolved
ignore set so both honour the same ignore_files: layering.

editor.open gains an optional 1-based line argument: it converts the
line to a byte offset and sets the initial selection, enabling
click-to-line from search results.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

lib/main.dart

@@ -37,6 +37,7 @@ import 'package:clide/src/daemon/pane_commands.dart';
 import 'package:clide/src/daemon/panel_commands.dart';
 import 'package:clide/src/daemon/panel_resizer_kernel.dart';
 import 'package:clide/src/daemon/pql_commands.dart';
+import 'package:clide/src/daemon/search_commands.dart';
 import 'package:clide/src/editor/registry.dart' show EditorRegistry;
 import 'package:clide/src/git/client.dart';
 import 'package:clide/src/cli/argv_dispatch.dart';
@@ -166,6 +167,14 @@ Future<void> main() async {
     registerPaneCommands(dispatcher, paneRegistry);
     final filesService = FilesService(root: workRoot, events: eventSink);
     registerFilesCommands(dispatcher, filesService);
+    // Search reuses the files service's resolved ignore set so the
+    // grep honours the same ignore_files: layering (D-4 / D-79).
+    final searchService = SearchService(
+      root: workRoot,
+      ignore: filesService.ignore,
+      events: eventSink,
+    );
+    registerSearchCommands(dispatcher, searchService);
     final editorRegistry = EditorRegistry(events: eventSink, workspaceRoot: workRoot);
     registerEditorCommands(dispatcher, editorRegistry);
     final gitClient = GitClient(toolchain: tc, workDir: workRoot);