docs: Update CHANGELOG.md (v1.0.4 entry) + ACTIVE_CONTEXT.md

CHANGELOG now includes diagnostic builds. ACTIVE_CONTEXT reflects
full session state for Chronicler pickup.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

services/rules-mod/CHANGELOG.md

@@ -1,5 +1,17 @@
 # Rules Mod Changelog
 
+## [1.0.4] - 2026-04-13 *(diagnostic build — 1.20.1 only)*
+
+### Added
+- INFO-level `[DIAG]` logging in RulesCommand: token length, channel ID, message ID, isValid result on every `/rules` invocation
+- INFO-level `[DIAG]` logging in DiscordFetcher: fetch attempt start, raw messageId on validation failure, HTTP target URL
+- Purpose: trace exactly where the config-to-fetch pipeline breaks on Otherworld
+
+### Note
+- Only `firefrostrules-1.0.4-1.20.1-forge.jar` was built. Other versions remain at 1.0.3.
+
+---
+
 ## [1.0.3] - 2026-04-13
 
 ### Fixed