feat: add /insights command with usage analytics and cost estimation

Inspired by Claude Code's /insights, adapted for Hermes Agent's multi-platform
architecture. Analyzes session history from state.db to produce comprehensive
usage insights.

Features:
- Overview stats: sessions, messages, tokens, estimated cost, active time
- Model breakdown: per-model sessions, tokens, and cost estimation
- Platform breakdown: CLI vs Telegram vs Discord etc. (unique to Hermes)
- Tool usage ranking: most-used tools with percentages
- Activity patterns: day-of-week chart, peak hours, streaks
- Notable sessions: longest, most messages, most tokens, most tool calls
- Cost estimation: real pricing data for 25+ models (OpenAI, Anthropic,
  DeepSeek, Google, Meta) with fuzzy model name matching
- Configurable time window: --days flag (default 30)
- Source filtering: --source flag to filter by platform

Three entry points:
- /insights slash command in CLI (supports --days and --source flags)
- /insights slash command in gateway (compact markdown format)
- hermes insights CLI subcommand (standalone)

Includes 56 tests covering pricing helpers, format helpers, empty DB,
populated DB with multi-platform data, filtering, formatting, and edge cases.

hermes_cli/commands.py

@@ -28,6 +28,7 @@ COMMANDS = {
     "/verbose": "Cycle tool progress display: off → new → all → verbose",
     "/compress": "Manually compress conversation context (flush memories + summarize)",
     "/usage": "Show token usage for the current session",
+    "/insights": "Show usage insights and analytics (last 30 days)",
     "/quit": "Exit the CLI (also: /exit, /q)",
 }
 

hermes_cli/main.py

@@ -1610,6 +1610,32 @@ For more help on a command:
 
     sessions_parser.set_defaults(func=cmd_sessions)
 
+    # =========================================================================
+    # insights command
+    # =========================================================================
+    insights_parser = subparsers.add_parser(
+        "insights",
+        help="Show usage insights and analytics",
+        description="Analyze session history to show token usage, costs, tool patterns, and activity trends"
+    )
+    insights_parser.add_argument("--days", type=int, default=30, help="Number of days to analyze (default: 30)")
+    insights_parser.add_argument("--source", help="Filter by platform (cli, telegram, discord, etc.)")
+
+    def cmd_insights(args):
+        try:
+            from hermes_state import SessionDB
+            from agent.insights import InsightsEngine
+
+            db = SessionDB()
+            engine = InsightsEngine(db)
+            report = engine.generate(days=args.days, source=args.source)
+            print(engine.format_terminal(report))
+            db.close()
+        except Exception as e:
+            print(f"Error generating insights: {e}")
+
+    insights_parser.set_defaults(func=cmd_insights)
+
     # =========================================================================
     # version command
     # =========================================================================