feat: /goal — persistent cross-turn goals (Ralph loop) (#18262)

Add a standing-goal slash command that keeps Hermes working toward a
user-stated objective across turns until it is achieved, paused, or
the turn budget runs out. Our take on the Ralph loop — cf. Codex CLI
0.128.0's /goal.

After each turn, a lightweight auxiliary-model judge call asks 'is
this goal satisfied by the assistant's last response?'. If not, and
we're under the turn budget (default 20), Hermes feeds a continuation
prompt back into the same session as a normal user message. Any real
user message preempts the continuation loop automatically.

Judge failures fail OPEN (continue) so a flaky judge never wedges
progress — the turn budget is the real backstop.

### Commands

- `/goal <text>`    — set a standing goal (kicks off the first turn)
- `/goal` or `/goal status` — show current state
- `/goal pause`    — pause the continuation loop
- `/goal resume`   — resume (resets turn counter)
- `/goal clear`    — drop the goal

Works on both CLI and gateway platforms via the central CommandDef
registry.

### Design invariants preserved

- **Prompt cache**: continuation prompts are regular user-role
  messages appended to history. No system-prompt mutation, no toolset
  swap.
- **Role alternation**: continuation is a user turn, never injected
  mid-tool-loop.
- **Session persistence**: goal state lives in SessionDB.state_meta
  keyed by `goal:<session_id>`, so `/resume` picks it up.
- **Mid-run safety**: on the gateway, `/goal status|pause|clear` are
  allowed mid-run (control-plane only); setting a new goal requires
  `/stop` first so we don't race a second continuation prompt against
  the current turn.

### Files

- `hermes_cli/goals.py` (new, 380 lines) — GoalManager + judge + state
- `hermes_cli/commands.py` — CommandDef entry
- `hermes_cli/config.py` — `goals.max_turns` default
- `hermes_cli/web_server.py` — dashboard category merge
- `cli.py` — /goal handler + post-turn continuation hook in
  process_loop
- `gateway/run.py` — /goal handler + post-turn continuation hook
  wrapping _handle_message_with_agent
- `tests/hermes_cli/test_goals.py` (new, 26 tests) — judge parsing,
  fail-open semantics, lifecycle, persistence, budget exhaustion
- `website/docs/reference/slash-commands.md` — docs entry

hermes_cli/config.py

@@ -952,7 +952,23 @@ DEFAULT_CONFIG = {
     # injected at the start of every API call for few-shot priming.
     # Never saved to sessions, logs, or trajectories.
     "prefill_messages_file": "",
-    
+
+    # Goals — persistent cross-turn goals (Ralph-style loop).
+    # After every turn, a lightweight judge call asks the auxiliary model
+    # whether the active /goal is satisfied by the assistant's last
+    # response. If not, Hermes feeds a continuation prompt back into the
+    # same session and keeps working until the goal is done, the turn
+    # budget is exhausted, or the user pauses/clears it. Judge failures
+    # fail OPEN (continue) so a flaky judge never wedges progress — the
+    # turn budget is the real backstop.
+    "goals": {
+        # Max continuation turns before Hermes auto-pauses the goal and
+        # asks the user to /goal resume. Protects against judge false
+        # negatives (goal actually done but judge says continue) and
+        # unbounded model spend on fuzzy / unachievable goals.
+        "max_turns": 20,
+    },
+
     # Skills — external skill directories for sharing skills across tools/agents.
     # Each path is expanded (~, ${VAR}) and resolved.  Read-only — skill creation
     # always goes to ~/.hermes/skills/.