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, 26 insertions, 4 deletions

diff --git a/internal/color/brush/brush.go b/internal/color/brush/brush.go
index 63d63d8..1400d4e 100644
--- a/internal/color/brush/brush.go
+++ b/internal/color/brush/brush.go
@@ -37,6 +37,13 @@ func paintSeverity(sb *strings.Builder, text string) bool {
 
 func paintRemote(sb *strings.Builder, line string) {
 	splitted := strings.SplitN(line, protocol.FieldDelimiter, 6)
+	if len(splitted) < 6 {
+		// Malformed or short frame (e.g. from an older/buggy server):
+		// fall back to the plain-text default branch instead of
+		// indexing out of range.
+		paintDefault(sb, line)
+		return
+	}
 
 	color.PaintWithAttr(sb, splitted[0],
 		config.Client.TermColors.Remote.RemoteFg,
@@ -105,6 +112,10 @@ func paintRemote(sb *strings.Builder, line string) {
 
 func paintClient(sb *strings.Builder, line string) {
 	splitted := strings.SplitN(line, protocol.FieldDelimiter, 3)
+	if len(splitted) < 3 {
+		paintDefault(sb, line)
+		return
+	}
 
 	color.PaintWithAttr(sb, splitted[0],
 		config.Client.TermColors.Client.ClientFg,
@@ -138,6 +149,10 @@ func paintClient(sb *strings.Builder, line string) {
 
 func paintServer(sb *strings.Builder, line string) {
 	splitted := strings.SplitN(line, protocol.FieldDelimiter, 3)
+	if len(splitted) < 3 {
+		paintDefault(sb, line)
+		return
+	}
 
 	color.PaintWithAttr(sb, splitted[0],
 		config.Client.TermColors.Server.ServerFg,
@@ -185,10 +200,17 @@ func Colorfy(line string) string {
 		paintServer(sb, line)
 
 	default:
-		color.PaintWithAttr(sb, line,
-			color.FgDefault,
-			color.BgDefault,
-			color.AttrNone)
+		paintDefault(sb, line)
 	}
 	return sb.String()
 }
+
+// paintDefault writes the line using the default (uncoloured) attributes.
+// It is the fallback used both by Colorfy's default branch and by the
+// paint* functions when the protocol frame is too short to decode safely.
+func paintDefault(sb *strings.Builder, line string) {
+	color.PaintWithAttr(sb, line,
+		color.FgDefault,
+		color.BgDefault,
+		color.AttrNone)
+}