feat: DTail fork — server/client feature development

Squashed development of the snonux/dtail fork's product code (internal/, cmd/)
since diverging from mimecast/dtail. Major areas:

- Read/output path: the former "turbo" channel-less path is now the single,
  default server-side read/output path for cat/grep/tail and MapReduce; the old
  channel-based path and its config/env toggles were removed.
- MapReduce: single aggregate implementation (server + serverless) fed directly
  by a processor pipeline, with input-exhausted finalization via the shutdown
  coordinator; high-concurrency and data-race fixes.
- Journal source reads (journal:unit.service) via journalctl, Linux-gated behind
  a journal-v1 capability.
- Auth-key fast reconnect: in-memory per-user public-key cache with TTL/max-keys,
  registered over an authenticated session (AUTHKEY), checked before
  authorized_keys.
- Interactive query reload (--interactive-query) with SESSION START/UPDATE
  generation boundaries and capability negotiation.
- Client-side deadlines: --timeout / --shutdownAfter as context deadlines;
  follow shutdown handling.
- Client logging: diagnostics-only daily log by default, opt-in payload tee via
  --log-payload.
- Numerous correctness fixes (buffer-pool double-recycle races, EOF-sentinel
  leaks, glob-expansion cap, TOCTOU in CSV parsing) with accompanying unit tests.

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

1 files changed, 113 insertions, 0 deletions

diff --git a/internal/mapr/groupsetresult_renderer_test.go b/internal/mapr/groupsetresult_renderer_test.go
new file mode 100644
index 0000000..53f45d5
--- /dev/null
+++ b/internal/mapr/groupsetresult_renderer_test.go
@@ -0,0 +1,113 @@
+package mapr
+
+import (
+	"strings"
+	"testing"
+)
+
+func TestGroupSetResultUsesProvidedRenderer(t *testing.T) {
+	query, err := NewQuery("select host,count(value) from stats group by host order by count(value)")
+	if err != nil {
+		t.Fatalf("Unable to parse query: %v", err)
+	}
+
+	groupSet := NewGroupSet()
+	set := groupSet.GetSet("host-a")
+	if err := set.Aggregate("host", Last, "host-a", false); err != nil {
+		t.Fatalf("Unable to aggregate host field: %v", err)
+	}
+	if err := set.Aggregate("count(value)", Count, "", false); err != nil {
+		t.Fatalf("Unable to aggregate count field: %v", err)
+	}
+
+	renderer := &recordingRenderer{}
+	result, numRows, err := groupSet.Result(query, 10, renderer)
+	if err != nil {
+		t.Fatalf("Unable to render result: %v", err)
+	}
+	if numRows != 1 {
+		t.Fatalf("Expected one row, got %d", numRows)
+	}
+	if len(renderer.headerCalls) != 2 {
+		t.Fatalf("Expected two header calls, got %d", len(renderer.headerCalls))
+	}
+	if renderer.headerCalls[0].isSortKey || !renderer.headerCalls[0].isGroupKey {
+		t.Fatalf("Unexpected flags for group key header: %+v", renderer.headerCalls[0])
+	}
+	if !renderer.headerCalls[1].isSortKey || renderer.headerCalls[1].isGroupKey {
+		t.Fatalf("Unexpected flags for sort key header: %+v", renderer.headerCalls[1])
+	}
+	if len(renderer.headerDelimiters) == 0 {
+		t.Fatal("Expected header delimiters to be rendered")
+	}
+	if len(renderer.dataDelimiters) == 0 {
+		t.Fatal("Expected data delimiters to be rendered")
+	}
+	if !strings.Contains(result, "host-a") || !strings.Contains(result, "1") {
+		t.Fatalf("Expected rendered output to contain row data, got %q", result)
+	}
+}
+
+func TestGroupSetResultFallsBackToPlainRenderer(t *testing.T) {
+	query, err := NewQuery("select count(value) from stats")
+	if err != nil {
+		t.Fatalf("Unable to parse query: %v", err)
+	}
+
+	groupSet := NewGroupSet()
+	set := groupSet.GetSet("")
+	if err := set.Aggregate("count(value)", Count, "", false); err != nil {
+		t.Fatalf("Unable to aggregate count field: %v", err)
+	}
+
+	result, numRows, err := groupSet.Result(query, 10, nil)
+	if err != nil {
+		t.Fatalf("Unable to render result with nil renderer: %v", err)
+	}
+	if numRows != 1 {
+		t.Fatalf("Expected one row, got %d", numRows)
+	}
+	if !strings.Contains(result, "count(value)") || !strings.Contains(result, "1") {
+		t.Fatalf("Expected plain rendered output, got %q", result)
+	}
+	if strings.Contains(result, "\x1b[") {
+		t.Fatalf("Expected plain output without ANSI escapes, got %q", result)
+	}
+}
+
+type recordingRenderer struct {
+	headerCalls      []headerCall
+	headerDelimiters []string
+	dataEntries      []string
+	dataDelimiters   []string
+}
+
+type headerCall struct {
+	text       string
+	isSortKey  bool
+	isGroupKey bool
+}
+
+func (r *recordingRenderer) WriteHeaderEntry(sb *strings.Builder, text string, isSortKey, isGroupKey bool) {
+	r.headerCalls = append(r.headerCalls, headerCall{
+		text:       text,
+		isSortKey:  isSortKey,
+		isGroupKey: isGroupKey,
+	})
+	sb.WriteString(text)
+}
+
+func (r *recordingRenderer) WriteHeaderDelimiter(sb *strings.Builder, text string) {
+	r.headerDelimiters = append(r.headerDelimiters, text)
+	sb.WriteString(text)
+}
+
+func (r *recordingRenderer) WriteDataEntry(sb *strings.Builder, text string) {
+	r.dataEntries = append(r.dataEntries, text)
+	sb.WriteString(text)
+}
+
+func (r *recordingRenderer) WriteDataDelimiter(sb *strings.Builder, text string) {
+	r.dataDelimiters = append(r.dataDelimiters, text)
+	sb.WriteString(text)
+}