#23757: docs: replace outdated legacy names and paths

## Summary - Replace legacy project names ("Clawd", "Pi") with "the agent" in `docs/channels/group-messages.md` - Fix outdated path `~/.clawdbot/.env` → `~/.openclaw/.env` in `docs/providers/together.md` ## Test plan - [x] Verify the docs render correctly on Mintlify <!-- greptile_comment --> <h3>Greptile Summary</h3> This PR completes documentation cleanup by replacing legacy project names ("Clawd", "Pi") with "the agent" and updating an outdated configuration path from `~/.clawdbot/.env` to `~/.openclaw/.env`. The changes are purely cosmetic and align with the project's rebranding to OpenClaw. <h3>Confidence Score: 5/5</h3> - This PR is safe to merge with no risk - The changes are documentation-only text replacements with no code or configuration logic changes. All replacements are accurate and consistent with the project's naming conventions. - No files require special attention _{Last reviewed commit: 852cdc9} <!-- greptile_other_comments_section --> _{(3/5) Reply to the agent's comments like "Can you suggest a fix for this @greptileai?" or ask follow-up questions!} <!-- /greptile_comment -->