docs(changelog): add diffs entry

CHANGELOG.md

@@ -11,6 +11,7 @@ Docs: https://docs.openclaw.ai
 - Discord/Thread bindings: replace fixed TTL lifecycle with inactivity (`idleHours`, default 24h) plus optional hard `maxAgeHours` lifecycle controls, and add `/session idle` + `/session max-age` commands for focused thread-bound sessions. (#27845) Thanks @osolmaz.
 - Web UI/i18n: add German (`de`) locale support and auto-render language options from supported locale constants in Overview settings. (#28495) thanks @dsantoreis.
 - Web UI/Cron i18n: localize cron page labels, filters, form help text, and validation/error messaging in English and zh-CN. (#29315) Thanks @BUGKillerKing.
+- Tools/Diffs: add a new optional `diffs` plugin tool for read-only diff rendering from before/after text or unified patches, with gateway viewer URLs for canvas and PNG image output. Thanks @gumadeiras.
 - Android/Gateway capability refresh: add live Android capability integration coverage and node canvas capability refresh wiring, plus runtime hardening for A2UI readiness retries, scoped canvas URL normalization, debug diagnostics JSON, and JavaScript MIME delivery. (#28388) Thanks @obviyus.
 - Feishu/Docx tables + uploads: add `feishu_doc` actions for Docx table creation/cell writing (`create_table`, `write_table_cells`, `create_table_with_values`) and image/file uploads (`upload_image`, `upload_file`) with stricter create/upload error handling for missing `document_id` and placeholder cleanup failures. (#20304) Thanks @xuhao1.
 - Feishu/Reactions: add inbound `im.message.reaction.created_v1` handling, route verified reactions through synthetic inbound turns, and harden verification with timeout + fail-closed filtering so non-bot or unverified reactions are dropped. (#16716) Thanks @schumilin.