Add effort badge to chain summary

Snapshot the agent's effort onto the chain (like model) so it survives
reload, archive and shared chains, then show it in the chain-end meta line.

- ChainRecord.Effort + chains.effort column (TryAddColumn migration).
- CreateChain INSERT carries the value.
- ChatService snapshots agent.Effort at chain creation, but only for Claude
  models – OpenAI providers store '' so there is no misleading badge.
- Anthropic streaming + CLI done-events include effort for the live path.
- chat.js buildMetaBadges renders "Effort: <level>" after the model badge,
  only when a value is set.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

Services/DatabaseService.cs

@@ -197,6 +197,7 @@ public partial class DatabaseService
         TryAddColumn(conn, "sessions", "unity_mcp_token", "TEXT");
         TryAddColumn(conn, "messages", "tag", "TEXT");
         TryAddColumn(conn, "agents", "effort", "TEXT NOT NULL DEFAULT ''");
+        TryAddColumn(conn, "chains", "effort", "TEXT NOT NULL DEFAULT ''");
 
         // Migration: 1M-Suffix entfernen (Mai 2026). Seit März 2026 ist 1M-Context Default
         // bei Opus 4.6/4.7/4.8 + Sonnet 4.6 – kein "[1m]"-Suffix mehr nötig.