Documentation is incorrect or incomplete regarding quote escaping and regex-hint effectiveness

[shouze]

Parent epic: #146

Context and problem

No current documentation explains the double escaping layer, shell and GitHub, required to search for a literal quote character. The existing regex-hint example wrapping a single word in quotes is misleading, wrapping a single word in quotes has no filtering effect on GitHub's side, verified directly against the API.

Solution

• Document the verified working example for searching a literal quote character, with an explanation of the double escaping layer.
• Replace the misleading regex-hint example with one that has a demonstrable filtering effect, or clearly state that wrapping a single word in quotes has no effect.
• Add a troubleshooting section explaining why quotes do not filter as expected and how to fix a 422 error caused by unbalanced quotes.

Acceptance criteria

• Every command shown as an example in the documentation has been verified against the live GitHub API.
• A troubleshooting section for 422 errors caused by quotes is present.

Definition of done

• bun run docs:build succeeds locally
• Documentation reviewed for consistency with the behavior implemented in sub-issues 1 and 3

Files

• docs/usage/search-syntax.md
• README.md
• docs/reference/cli-options.md