feat(gateway): rename to tool_progress_grouping, add config/docs/tests

Follow-up to salvaged PR #41620:
- Rename tool_progress_style -> tool_progress_grouping (clearer intent)
- Add display.tool_progress_grouping to DEFAULT_CONFIG (accumulate default)
- Document in messaging docs incl. 'separate is noisier, only where progress enabled'
- Add resolver tests (default/global/override/invalid/case)

hermes_cli/config.py

@@ -1485,6 +1485,12 @@ DEFAULT_CONFIG = {
         "tool_progress_command": False,  # Enable /verbose command in messaging gateway
         "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)
+        # How gateway tool-progress is grouped on platforms that support message
+        # editing: "accumulate" (default) edits one bubble in place; "separate"
+        # sends one message per tool (the pre-v0.9 behavior, noisier). Only
+        # applies where tool_progress is already enabled. Per-platform override
+        # via display.platforms.<platform>.tool_progress_grouping.
+        "tool_progress_grouping": "accumulate",
         # Auto-delete system-notice replies (e.g. "✨ New session started!",
         # "♻ Restarting gateway…", "⚡ Stopped…") after N seconds on platforms
         # that support message deletion (currently Telegram; other platforms