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, 2 insertions, 2 deletions

diff --git a/internal/hexaiaction/custom_exec_more_test.go b/internal/hexaiaction/custom_exec_more_test.go
index d826b39..73d9839 100644
--- a/internal/hexaiaction/custom_exec_more_test.go
+++ b/internal/hexaiaction/custom_exec_more_test.go
@@ -19,7 +19,7 @@ func (c *capDoer) Chat(_ context.Context, msgs []llm.Message, _ ...llm.RequestOp
 func (*capDoer) DefaultModel() string { return "m" }
 
 func TestExecuteAction_Custom_DoesNotMutateProvidedSelection(t *testing.T) {
-	cfg := appconfig.Load(nil)
+	cfg := appconfig.Load(context.Background(), nil)
 	parts := InputParts{Selection: "code"}
 	selectedCustom := &appconfig.CustomAction{ID: "x", Title: "X", Instruction: "Do it"}
 	_, _ = executeAction(context.Background(), ActionCustom, parts, &cfg, fakeDoer{"OK"}, nil, selectedCustom)
@@ -29,7 +29,7 @@ func TestExecuteAction_Custom_DoesNotMutateProvidedSelection(t *testing.T) {
 }
 
 func TestRunCustom_UserTemplate_InjectsDiagnostics(t *testing.T) {
-	cfg := appconfig.Load(nil)
+	cfg := appconfig.Load(context.Background(), nil)
 	parts := InputParts{Selection: "code", Diagnostics: []string{"L1", "L2"}}
 	ca := appconfig.CustomAction{ID: "y", Title: "Y", User: "{{diagnostics}}\n{{selection}}"}
 	cap := &capDoer{}