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, 10 insertions, 0 deletions

diff --git a/internal/config/env.go b/internal/config/env.go
index 1ccac9c..2eff7b0 100644
--- a/internal/config/env.go
+++ b/internal/config/env.go
@@ -9,10 +9,20 @@ func Env(env string) bool {
 
 // Hostname returns the current hostname. It can be overriden with
 // DTAIL_HOSTNAME_OVERRIDE environment variable (useful for integration tests).
+// When DTAIL_INTEGRATION_TEST_RUN_MODE is set to "yes", it automatically
+// returns "integrationtest" as the hostname.
 func Hostname() (string, error) {
+	// Check if we're in integration test mode
+	if Env("DTAIL_INTEGRATION_TEST_RUN_MODE") {
+		return "integrationtest", nil
+	}
+	
+	// Check for manual hostname override
 	hostname := os.Getenv("DTAIL_HOSTNAME_OVERRIDE")
 	if len(hostname) > 0 {
 		return hostname, nil
 	}
+	
+	// Return actual hostname
 	return os.Hostname()
 }