feat: per-platform display verbosity configuration (#8006)

Add display.platforms section to config.yaml for per-platform overrides of
display settings (tool_progress, show_reasoning, streaming, tool_preview_length).

Each platform gets sensible built-in defaults based on capability tier:
- High (telegram, discord): tool_progress=all, streaming follows global
- Medium (slack, mattermost, matrix, feishu): tool_progress=new
- Low (signal, whatsapp, bluebubbles, wecom, etc.): tool_progress=off, streaming=false
- Minimal (email, sms, webhook, homeassistant): tool_progress=off, streaming=false

Example config:
  display:
    platforms:
      telegram:
        tool_progress: all
        show_reasoning: true
      slack:
        tool_progress: off

Resolution order: platform override > global setting > built-in platform default.

Changes:
- New gateway/display_config.py: resolver module with tier-based platform defaults
- gateway/run.py: tool_progress, tool_preview_length, streaming, show_reasoning
  all resolve per-platform via the new resolver
- /verbose command: now cycles tool_progress per-platform (saves to
  display.platforms.<platform>.tool_progress instead of global)
- /reasoning show|hide: now saves show_reasoning per-platform
- Config version 15 -> 16: migrates tool_progress_overrides into display.platforms
- Backward compat: legacy tool_progress_overrides still read as fallback
- 27 new tests for resolver, normalization, migration, backward compat
- Updated verbose command tests for per-platform behavior

Addresses community request for per-channel verbosity control (Guillaume Meyer,
Nathan Danielsen) — high verbosity on backchannel Telegram, low on customer-facing
Slack, none on email.

hermes_cli/config.py

@@ -517,8 +517,9 @@ DEFAULT_CONFIG = {
         "skin": "default",
         "interim_assistant_messages": True,  # Gateway: show natural mid-turn assistant status messages
         "tool_progress_command": False,  # Enable /verbose command in messaging gateway
-        "tool_progress_overrides": {},  # Per-platform overrides: {"signal": "off", "telegram": "all"}
+        "tool_progress_overrides": {},  # DEPRECATED — use display.platforms instead
         "tool_preview_length": 0,  # Max chars for tool call previews (0 = no limit, show full paths/commands)
+        "platforms": {},  # Per-platform display overrides: {"telegram": {"tool_progress": "all"}, "slack": {"tool_progress": "off"}}
     },
 
     # Privacy settings
@@ -706,7 +707,7 @@ DEFAULT_CONFIG = {
     },
 
     # Config schema version - bump this when adding new required fields
-    "_config_version": 15,
+    "_config_version": 16,
 }
 
 # =============================================================================
@@ -1947,6 +1948,30 @@ def migrate_config(interactive: bool = True, quiet: bool = False) -> Dict[str, A
             if not quiet:
                 print("  ✓ Added display.interim_assistant_messages=true")
 
+    # ── Version 15 → 16: migrate tool_progress_overrides into display.platforms ──
+    if current_ver < 16:
+        config = read_raw_config()
+        display = config.get("display", {})
+        if not isinstance(display, dict):
+            display = {}
+        old_overrides = display.get("tool_progress_overrides")
+        if isinstance(old_overrides, dict) and old_overrides:
+            platforms = display.get("platforms", {})
+            if not isinstance(platforms, dict):
+                platforms = {}
+            for plat, mode in old_overrides.items():
+                if plat not in platforms:
+                    platforms[plat] = {}
+                if "tool_progress" not in platforms[plat]:
+                    platforms[plat]["tool_progress"] = mode
+            display["platforms"] = platforms
+            config["display"] = display
+            save_config(config)
+            if not quiet:
+                migrated = ", ".join(f"{p}={m}" for p, m in old_overrides.items())
+                print(f"  ✓ Migrated tool_progress_overrides → display.platforms: {migrated}")
+            results["config_added"].append("display.platforms (migrated from tool_progress_overrides)")
+
     if current_ver < latest_ver and not quiet:
         print(f"Config version: {current_ver} → {latest_ver}")