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, 60 insertions, 0 deletions

diff --git a/cmd/dtail-tools/main.go b/cmd/dtail-tools/main.go
new file mode 100644
index 0000000..2b96a56
--- /dev/null
+++ b/cmd/dtail-tools/main.go
@@ -0,0 +1,60 @@
+package main
+
+import (
+	"fmt"
+	"os"
+
+	"github.com/mimecast/dtail/internal/tools/benchmark"
+	"github.com/mimecast/dtail/internal/tools/pgo"
+	"github.com/mimecast/dtail/internal/tools/profile"
+)
+
+func main() {
+	if len(os.Args) < 2 {
+		printUsage()
+		os.Exit(1)
+	}
+
+	command := os.Args[1]
+	
+	// Remove command from args for subcommand parsing
+	os.Args = append([]string{os.Args[0]}, os.Args[2:]...)
+
+	switch command {
+	case "profile":
+		if err := profile.Run(); err != nil {
+			fmt.Fprintf(os.Stderr, "Error: %v\n", err)
+			os.Exit(1)
+		}
+	case "benchmark":
+		if err := benchmark.Run(); err != nil {
+			fmt.Fprintf(os.Stderr, "Error: %v\n", err)
+			os.Exit(1)
+		}
+	case "pgo":
+		if err := pgo.Run(); err != nil {
+			fmt.Fprintf(os.Stderr, "Error: %v\n", err)
+			os.Exit(1)
+		}
+	case "help", "-h", "--help":
+		printUsage()
+	default:
+		fmt.Fprintf(os.Stderr, "Unknown command: %s\n", command)
+		printUsage()
+		os.Exit(1)
+	}
+}
+
+func printUsage() {
+	fmt.Println("dtail-tools - DTail performance analysis toolkit")
+	fmt.Println()
+	fmt.Println("Usage: dtail-tools <command> [options]")
+	fmt.Println()
+	fmt.Println("Commands:")
+	fmt.Println("  profile    Run profiling on dtail commands")
+	fmt.Println("  benchmark  Run benchmarks and manage baselines")
+	fmt.Println("  pgo        Profile-Guided Optimization for dtail commands")
+	fmt.Println("  help       Show this help message")
+	fmt.Println()
+	fmt.Println("Run 'dtail-tools <command> -h' for command-specific help")
+}
\ No newline at end of file