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, 77 insertions, 0 deletions

diff --git a/internal/mapr/token_test.go b/internal/mapr/token_test.go
new file mode 100644
index 0000000..6ba7b3a
--- /dev/null
+++ b/internal/mapr/token_test.go
@@ -0,0 +1,77 @@
+package mapr
+
+import "testing"
+
+// TestTokensConsumeBacktickStripping covers the backtick-stripping path in
+// tokensConsume, including the regression for a lone backtick token which
+// previously panicked with "slice bounds out of range [1:0]".
+func TestTokensConsumeBacktickStripping(t *testing.T) {
+	type expected struct {
+		str            string
+		quotesStripped bool
+	}
+	tests := []struct {
+		name  string
+		input string
+		want  []expected
+	}{
+		{
+			name:  "empty string",
+			input: "",
+			want:  nil,
+		},
+		{
+			name:  "single backtick",
+			input: "`",
+			want:  []expected{{str: "`", quotesStripped: false}},
+		},
+		{
+			name:  "double backtick",
+			input: "``",
+			want:  []expected{{str: "", quotesStripped: true}},
+		},
+		{
+			name:  "backtick quoted identifier",
+			input: "`x`",
+			want:  []expected{{str: "x", quotesStripped: true}},
+		},
+		{
+			name:  "unterminated backtick",
+			input: "`foo",
+			want:  []expected{{str: "`foo", quotesStripped: false}},
+		},
+		{
+			name:  "regular identifier",
+			input: "foo",
+			want:  []expected{{str: "foo", quotesStripped: false}},
+		},
+	}
+
+	for _, tc := range tests {
+		t.Run(tc.name, func(t *testing.T) {
+			defer func() {
+				if r := recover(); r != nil {
+					t.Fatalf("tokenize/tokensConsume panicked on %q: %v", tc.input, r)
+				}
+			}()
+
+			tokens := tokenize(tc.input)
+			_, got := tokensConsume(tokens)
+
+			if len(got) != len(tc.want) {
+				t.Fatalf("input %q: got %d tokens, want %d (tokens=%v)",
+					tc.input, len(got), len(tc.want), got)
+			}
+			for i, w := range tc.want {
+				if got[i].str != w.str {
+					t.Errorf("input %q token %d: str=%q, want %q",
+						tc.input, i, got[i].str, w.str)
+				}
+				if got[i].quotesStripped != w.quotesStripped {
+					t.Errorf("input %q token %d: quotesStripped=%v, want %v",
+						tc.input, i, got[i].quotesStripped, w.quotesStripped)
+				}
+			}
+		})
+	}
+}