Thread context.Context through blocking I/O entry points

Accept ctx as the first parameter on the blocking I/O entry points and
propagate it to downstream blocking calls so the work is cancellable from
the process entry point:

- appconfig.Load / LoadWithOptions: honor ctx before the blocking file
  reads, returning defaults on a cancelled context.
- LSP: lsp.Server.Run(ctx) ties the serve loop to the caller context via a
  new watchParentContext bridge (cancels the server context, aborting
  in-flight LLM work). Threaded through hexailsp.Run/RunWithConfig/
  RunWithFactory and runtimeconfig.Store.Reload.
- MCP: mcp.Server.Run(ctx) stops accepting requests once ctx is cancelled;
  threaded through hexaimcp.Run/RunWithFactory/RunBackfill.
- editor: RunEditor/OpenTempAndEdit/OpenFile take ctx and use
  exec.CommandContext so a cancelled context kills the editor subprocess;
  threaded through hexaicli, hexaiaction and askcli call sites.

Top-level callers (cmd/hexai-lsp-server, cmd/hexai-mcp-server) now build a
signal-cancelled context (SIGINT/SIGTERM) so shutdown tears the run down
cleanly. Updated comments to explain the cancellation flow and added
cancellation tests for the LSP/MCP loops, editor, and config load.

All tests pass with -race; cross-package coverage 86.2%.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

1 files changed, 4 insertions, 2 deletions

diff --git a/internal/hexaicli/editor_integration_test.go b/internal/hexaicli/editor_integration_test.go
index 7d53d1f..e5580be 100644
--- a/internal/hexaicli/editor_integration_test.go
+++ b/internal/hexaicli/editor_integration_test.go
@@ -28,7 +28,9 @@ func TestRun_NoArgs_OpensEditor(t *testing.T) {
 	newClientFromApp = func(_ appconfig.App) (llm.Client, error) { return cliFake{}, nil }
 	t.Cleanup(func() { newClientFromApp = oldNew })
 	oldRun := editor.RunEditor
-	editor.RunEditor = func(_ string, path string) error { return os.WriteFile(path, []byte("PROMPT"), 0o600) }
+	editor.RunEditor = func(_ context.Context, _ string, path string) error {
+		return os.WriteFile(path, []byte("PROMPT"), 0o600)
+	}
 	t.Cleanup(func() { editor.RunEditor = oldRun })
 	t.Setenv("HEXAI_EDITOR", "dummy")
 
@@ -50,7 +52,7 @@ func TestRun_WithArgs_DoesNotOpenEditor(t *testing.T) {
 	// Stub editor and detect if called (should not be)
 	called := false
 	oldRun := editor.RunEditor
-	editor.RunEditor = func(_ string, _ string) error { called = true; return nil }
+	editor.RunEditor = func(_ context.Context, _ string, _ string) error { called = true; return nil }
 	t.Cleanup(func() { editor.RunEditor = oldRun })
 	var stdout, stderr bytes.Buffer
 	if err := Run(context.Background(), []string{"ARG"}, bytes.NewBufferString("SEL"), &stdout, &stderr); err != nil {