### What problem does this PR solve?
This fixes two broken internal documentation links in the guides:
- `docs/develop/mcp/launch_mcp_server.md` linked
`./acquire_ragflow_api_key.md`, but the target page lives one level up
as `../acquire_ragflow_api_key.md`.
- `docs/guides/dataset/run_retrieval_test.md` linked
`./construct_knowledge_graph.md`, but the actual page lives under
`./advanced/construct_knowledge_graph.md`.
These broken links make it harder to follow the MCP and retrieval-test
docs from the local docs tree.
### Type of change
- [ ] Bug Fix (non-breaking change which fixes an issue)
- [ ] New Feature (non-breaking change which adds functionality)
- [x] Documentation Update
- [ ] Refactoring
- [ ] Performance Improvement
- [ ] Other (please describe):
### What problem does this PR solve?
Trailing white-spaces in commit 6814ace1aa
got automatically trimmed by code editor may causes documentation
typesetting broken.
Mostly for double spaces for soft line breaks.
### Type of change
- [x] Documentation Update
### What problem does this PR solve?
Update icons for docs.
Trailing spaces are auto truncated by the editor, does not affect real
content.
### Type of change
- [x] Documentation Update
### What problem does this PR solve?
### Type of change
- [x] Documentation Update
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Co-authored-by: balibabu <cike8899@users.noreply.github.com>
