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, 4 insertions, 1 deletions

diff --git a/internal/mapr/logformat/custom1.go b/internal/mapr/logformat/custom1.go
index 7229f3e..a159328 100644
--- a/internal/mapr/logformat/custom1.go
+++ b/internal/mapr/logformat/custom1.go
@@ -2,15 +2,18 @@ package logformat
 
 import "errors"
 
+// ErrCustom1NotImplemented indicates custom1 parser is only a template.
 var ErrCustom1NotImplemented error = errors.New("custom1 log format is not implemented")
 
 // Template for creating a custom log format.
 type custom1Parser struct{}
 
+var _ Parser = (*custom1Parser)(nil)
+
 func newCustom1Parser(hostname, timeZoneName string, timeZoneOffset int) (*custom1Parser, error) {
 	return &custom1Parser{}, ErrCustom1NotImplemented
 }
 
-func (p *custom1Parser) MakeFields(maprLine string) (map[string]string, error) {
+func (p *custom1Parser) MakeFields(maprLine, _ string) (map[string]string, error) {
 	return nil, ErrCustom1NotImplemented
 }