Review-assist for #323 under the Bitgesell improvement queue (#81):

• Scope is narrow and useful: test/lint/check-doc.py shells out through formatted command strings, so quoting the resolved source-tree path is the right fix for checkouts stored under paths with spaces.
• Please keep one validation example that actually runs from a path containing a space, even if only documented in the PR body, because the normal python3 test/lint/check-doc.py run from a no-space checkout does not exercise the regression.
• The quoted value flows through three grep commands. Before merge, I would confirm the -- <path> ':(exclude)src/test/' argument order still behaves as intended on the project-supported shell environment.
• This change intentionally quotes only the source path, not the exclude path. That is probably fine because FOLDER_TEST is repo-relative and static, but it is worth preserving that assumption in the review notes.
• For BGL (Bitgesell) Bounty/Improvement Program ($50000 budget) #81 payout hygiene, this looks like a small CI/lint portability fix rather than a broad feature; I would count it only after maintainers confirm this class of test hardening is eligible.

I only reviewed the public diff. No duplicate implementation PR, live-chain action, secret material, dependency install, or payment action from me here.