feat: display previous messages when resuming a session in CLI

When resuming a session via --continue or --resume, show a compact recap
of the previous conversation inside a Rich panel before the input prompt.
This gives users immediate visual context about what was discussed.

Changes:
- Add _preload_resumed_session() to load session history early (in run(),
  before banner) so _init_agent() doesn't need a separate DB round-trip
- Add _display_resumed_history() that renders a formatted recap panel:
  * User messages shown with gold bullet (truncated at 300 chars)
  * Assistant responses shown with green diamond (truncated at 200 chars / 3 lines)
  * Tool calls collapsed to count + tool names
  * System messages and tool results hidden
  * <REASONING_SCRATCHPAD> blocks stripped from display
  * Pure-reasoning messages (no visible output) skipped entirely
  * Capped at last 10 exchanges with 'N earlier messages' indicator
  * Dim/muted styling distinguishes recap from active conversation
- Add display.resume_display config option: 'full' (default) or 'minimal'
- Store resume_display as instance variable (like compact) for testability
- 27 new tests covering all display scenarios, config, and edge cases

Closes #719

hermes_cli/config.py

@@ -92,6 +92,7 @@ DEFAULT_CONFIG = {
     "display": {
         "compact": False,
         "personality": "kawaii",
+        "resume_display": "full",  # "full" (show previous messages) | "minimal" (one-liner only)
     },
     
     # Text-to-speech configuration