feat: add Claude Opus 4.6 to built-in model catalog (#9853)

* feat: add Claude Opus 4.6 to built-in model catalog

- Update default model from claude-opus-4-5 to claude-opus-4-6
- Add opus-4.6 model ID normalization
- Add claude-opus-4-6 to live model filter prefixes
- Update image tool to prefer claude-opus-4-6 for vision
- Add CLI backend alias for opus-4.6
- Update onboard auth default selections to include opus-4.6
- Update model picker placeholder

Closes #9811

* test: update tests for claude-opus-4-6 default

- Fix model-alias-defaults test to use claude-opus-4-6
- Fix image-tool test to expect claude-opus-4-6 in fallbacks

* feat: support claude-opus-4-6

* docs: update changelog for opus 4.6 (#9853) (thanks @TinyTb)

* chore: bump pi to 0.52.0

---------

Co-authored-by: Slurpy <slurpy@openclaw.ai>
Co-authored-by: Peter Steinberger <steipete@gmail.com>

CHANGELOG.md

@@ -6,6 +6,7 @@ Docs: https://docs.openclaw.ai
 
 ### Changes
 
+- Models: default Anthropic model to `anthropic/claude-opus-4-6`. (#9853) Thanks @TinyTb.
 - Telegram: auto-inject forum topic `threadId` in message tool and subagent announce so media, buttons, and subagent results land in the correct topic instead of General. (#7235) Thanks @Lukavyi.
 - CLI: sort `openclaw --help` commands (and options) alphabetically. (#8068) Thanks @deepsoumya617.
 - Telegram: remove last `@ts-nocheck` from `bot-handlers.ts`, use Grammy types directly, deduplicate `StickerMetadata`. Zero `@ts-nocheck` remaining in `src/telegram/`. (#9206)