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, 18 insertions, 17 deletions

diff --git a/internal/mapr/token.go b/internal/mapr/token.go
index 77362f7..f287dbc 100644
--- a/internal/mapr/token.go
+++ b/internal/mapr/token.go
@@ -14,22 +14,7 @@ type token struct {
 	quotesStripped bool
 }
 
-func (t token) isKeyword() bool {
-	if !t.isBareword {
-		return false
-	}
-	for _, keyword := range keywords {
-		if strings.ToLower(t.str) == keyword {
-			return true
-		}
-	}
-	return false
-}
-
-func (t token) String() string {
-	return t.str
-}
-
+// tokenize parses a query string into tokens.
 func tokenize(queryStr string) []token {
 	var tokens []token
 	for i, part := range strings.Split(queryStr, "\"") {
@@ -68,7 +53,7 @@ func tokensConsume(tokens []token) ([]token, []token) {
 		if length == 0 {
 			continue
 		}
-		if t.str[0] == '`' && t.str[length-1] == '`' {
+		if length >= 2 && t.str[0] == '`' && t.str[length-1] == '`' {
 			stripped := t.str[1 : length-1]
 			//dlog.Common.Trace("stripped", stripped)
 			t := token{
@@ -105,3 +90,19 @@ func tokensConsumeOptional(tokens []token, optional string) []token {
 	}
 	return tokens
 }
+
+func (t token) isKeyword() bool {
+	if !t.isBareword {
+		return false
+	}
+	for _, keyword := range keywords {
+		if strings.ToLower(t.str) == keyword {
+			return true
+		}
+	}
+	return false
+}
+
+func (t token) String() string {
+	return t.str
+}