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, 3 insertions, 0 deletions

diff --git a/internal/config/common.go b/internal/config/common.go
index 7a72cfe..4e90f7e 100644
--- a/internal/config/common.go
+++ b/internal/config/common.go
@@ -4,6 +4,8 @@ package config
 type CommonConfig struct {
 	// The SSH port number
 	SSHPort int
+	// SSH connection timeout in milliseconds.
+	SSHConnectTimeoutMs int `json:",omitempty"`
 	// Enable experimental features (mainly for dev purposes)
 	ExperimentalFeaturesEnable bool `json:",omitempty"`
 	// LogDir defines the log directory.
@@ -22,6 +24,7 @@ type CommonConfig struct {
 func newDefaultCommonConfig() *CommonConfig {
 	return &CommonConfig{
 		SSHPort:                    DefaultSSHPort,
+		SSHConnectTimeoutMs:        2000,
 		ExperimentalFeaturesEnable: false,
 		LogDir:                     "log",
 		Logger:                     "stdout",