refactor(memory,skills): replace tri-state write_mode with boolean write_approval (default off) (#43354)

The shipped tri-state write_mode (on|off|approve) conflated two concepts —
whether writes are enabled and whether they're gated — so 'on' (writes flow
freely, gate inactive) read like 'gating is on'. Replace it with a single
clear boolean gate that defaults off.

  memory.write_approval / skills.write_approval:
    false (default) — write freely; the approval gate is off (pre-gate behaviour)
    true            — require approval: memory foreground prompts inline, memory
                      background-review + all skill writes stage for review

The old 'off = block all writes' mode is dropped; memory_enabled: false already
disables memory entirely, so a third 'block' state was redundant.

- tools/write_approval.py: get_write_mode/MODE_* → write_approval_enabled() bool;
  evaluate_gate() loses the config-driven 'blocked' path (blocked now only comes
  from an interactive user denial).
- tools/memory_tool.py, tools/skill_manager_tool.py: comment + behaviour follow.
- hermes_cli/config.py: memory/skills write_mode → write_approval (False);
  _config_version 28→29 with a 28→29 migration that renames any persisted
  write_mode (approve→true, on/off/unset→false) and drops the old key.
- slash commands: '/memory|/skills mode <on|off|approve>' → 'approval <on|off>'
  ('mode' kept as a back-compat alias); set_mode_fn callback now takes a bool.
- write_approval_commands.py, cli_commands_mixin.py, gateway/slash_commands.py,
  commands.py: handlers + registry args/subcommands updated.
- docs + tests rewritten for the boolean model; added migration tests.

hermes_cli/write_approval_commands.py

@@ -20,7 +20,10 @@ from typing import List, Optional
 
 from tools import write_approval as wa
 
-_VALID_MODES = (wa.MODE_ON, wa.MODE_OFF, wa.MODE_APPROVE)
+
+def _fmt_state(subsystem: str) -> str:
+    on = wa.write_approval_enabled(subsystem)
+    return f"{subsystem}.write_approval = {'on' if on else 'off'}"
 
 
 # ---------------------------------------------------------------------------
@@ -63,18 +66,17 @@ def handle_pending_subcommand(
         memory_store: live MemoryStore for applying approved memory writes
             (CLI passes ``self.agent._memory_store``; gateway applies against a
             freshly loaded store).
-        set_mode_fn: optional callable ``(mode: str) -> None`` that persists the
-            new write_mode to config (gateway provides this; CLI uses its own
-            ``save_config_value`` and passes a closure).
+        set_mode_fn: optional callable ``(enabled: bool) -> None`` that
+            persists the new write_approval boolean to config (gateway provides
+            this; CLI uses its own ``save_config_value`` and passes a closure).
 
     Returns a text string to show the user. Returns None when the args are not
     a write-approval subcommand (caller falls through to its other handling,
     e.g. /skills search).
     """
     if not args:
-        # Bare /memory or /skills with no sub → show pending + current mode.
-        mode = wa.get_write_mode(subsystem)
-        return f"{subsystem}.write_mode = {mode}\n\n" + _fmt_pending_list(subsystem)
+        # Bare /memory or /skills with no sub → show pending + gate state.
+        return f"{_fmt_state(subsystem)}\n\n" + _fmt_pending_list(subsystem)
 
     sub = args[0].lower()
     rest = args[1:]
@@ -91,8 +93,8 @@ def handle_pending_subcommand(
     if sub == "diff" and subsystem == wa.SKILLS:
         return _diff(rest)
 
-    if sub == "mode":
-        return _set_mode(subsystem, rest, set_mode_fn)
+    if sub in {"approval", "mode"}:  # 'mode' kept as a back-compat alias
+        return _set_approval(subsystem, rest, set_mode_fn)
 
     return None  # not ours — caller handles
 
@@ -179,19 +181,29 @@ def _diff(rest: List[str]) -> str:
     return header + "\n" + diff
 
 
-def _set_mode(subsystem: str, rest: List[str], set_mode_fn) -> str:
+def _set_approval(subsystem: str, rest: List[str], set_mode_fn) -> str:
+    """Turn the approval gate on/off for a subsystem.
+
+    ``set_mode_fn`` (when provided) persists the new boolean to config.
+    """
     if not rest:
-        cur = wa.get_write_mode(subsystem)
-        return (f"{subsystem}.write_mode = {cur}\n"
-                f"Set with: /{subsystem} mode <on|off|approve>")
-    mode = rest[0].lower()
-    if mode not in _VALID_MODES:
-        return f"Invalid mode '{mode}'. Use: on, off, approve."
+        return (f"{_fmt_state(subsystem)}\n"
+                f"Set with: /{subsystem} approval <on|off>")
+    arg = rest[0].strip().lower()
+    truthy = {"on", "true", "yes", "1", "enable", "enabled"}
+    falsey = {"off", "false", "no", "0", "disable", "disabled"}
+    if arg in truthy:
+        enabled = True
+    elif arg in falsey:
+        enabled = False
+    else:
+        return f"Invalid value '{arg}'. Use: on or off."
     if set_mode_fn is None:
-        return (f"To change {subsystem} write mode, run:\n"
-                f"  hermes config set {subsystem}.write_mode {mode}")
+        val = "true" if enabled else "false"
+        return (f"To change the {subsystem} approval gate, run:\n"
+                f"  hermes config set {subsystem}.write_approval {val}")
     try:
-        set_mode_fn(mode)
+        set_mode_fn(enabled)
     except Exception as e:
-        return f"Failed to set {subsystem}.write_mode: {e}"
-    return f"{subsystem}.write_mode set to '{mode}'."
+        return f"Failed to set {subsystem}.write_approval: {e}"
+    return f"{subsystem}.write_approval set to '{'on' if enabled else 'off'}'."