feat(commands): /compact alias + --preview/--dry-run flags for /compress (#3243 salvage)

Salvaged from PR #3243 by @Mibayy, reimplemented against current main
(the original diff targeted a removed gateway/run.py handler).

- /compact is now a first-class alias of /compress (CLI, gateway,
  Telegram/Slack/Discord command lists, autocomplete) — also fixes the
  dangling '/compact' references in gateway error messages
  (gateway/run.py context-exhausted banners).
- --preview / --dry-run: report what WOULD be compressed (message
  counts, token estimate, 'here [N]' boundary) without touching the
  transcript. Flags coexist with the existing 'here [N]' / focus-topic
  args on both the CLI and gateway surfaces via shared pure helpers in
  hermes_cli/partial_compress.py.
- --aggressive (LLM-free hard truncation) is intentionally NOT
  implemented: it would need its own transcript-persistence branch
  outside the guarded _compress_context rotation machinery (#44794
  data-loss class). The flag is recognized and returns an explanatory
  message pointing at '/compress here [N]' and /undo instead of being
  mis-parsed as a focus topic.
- locales: gateway.compress.aggressive_unsupported added to all 16
  catalogs (parity test enforced).
- release.py: AUTHOR_MAP entry for contributor credit.

cli.py

@@ -9314,9 +9314,11 @@ class HermesCLI(CLIAgentSetupMixin, CLICommandsMixin):
             return
 
         from hermes_cli.partial_compress import (
+            extract_compress_flags,
             parse_partial_compress_args,
             rejoin_compressed_head_and_tail,
             split_history_for_partial_compress,
+            summarize_compress_preview,
         )
 
         # Args after the command word (e.g. "/compress here 3" -> "here 3").
@@ -9326,9 +9328,42 @@ class HermesCLI(CLIAgentSetupMixin, CLICommandsMixin):
             if len(_parts) > 1:
                 raw_args = _parts[1].strip()
 
+        # Strip --preview/--dry-run/--aggressive before positional parsing
+        # so the flags coexist with 'here [N]' / focus-topic forms.
+        raw_args, preview, aggressive = extract_compress_flags(raw_args)
         partial, keep_last, focus_topic = parse_partial_compress_args(raw_args)
         focus_topic = focus_topic or ""
 
+        if aggressive:
+            # LLM-free hard truncation is not supported: it would need its
+            # own transcript-persistence path outside the guarded
+            # _compress_context rotation machinery. Surface that instead of
+            # silently mis-parsing the flag as a focus topic.
+            print("(._.) --aggressive is not supported; use '/compress here [N]' "
+                  "to keep only recent exchanges, or /undo to drop turns.")
+            if not preview:
+                return
+
+        if preview:
+            from agent.model_metadata import estimate_request_tokens_rough
+            _sys_prompt = getattr(self.agent, "_cached_system_prompt", "") or ""
+            _tools = getattr(self.agent, "tools", None) or None
+            approx_tokens = estimate_request_tokens_rough(
+                self.conversation_history,
+                system_prompt=_sys_prompt,
+                tools=_tools,
+            )
+            report = summarize_compress_preview(
+                self.conversation_history,
+                partial,
+                keep_last,
+                focus_topic or None,
+                approx_tokens,
+            )
+            for line in report["lines"]:
+                print(f"🗜️  {line}")
+            return
+
         original_count = len(self.conversation_history)
         with self._busy_command("Compressing context..."):
             try: