#6861: docs(tts): remove invisible AI citation markers

Removes 5 invisible Unicode citation markers (e.g. `citeturn2search0`) that were accidentally left in the TTS documentation from AI-generated content. These invisible characters don't affect rendering but pollute the source file. <!-- greptile_comment --> <h2>Greptile Overview</h2> <h3>Greptile Summary</h3> This PR cleans up `docs/tts.md` by removing five invisible Unicode “AI citation marker” tokens (e.g., `citeturn2search0`) that were accidentally left in the documentation. The change is purely documentation-source hygiene: it doesn’t alter any product behavior, but it prevents hidden characters from polluting diffs, search, and future edits. <h3>Confidence Score: 5/5</h3> - This PR is safe to merge; it only removes stray invisible characters from a documentation file. - The diff is limited to deleting five hidden Unicode marker sequences in `docs/tts.md` with no structural markdown changes and no code/runtime impact. - No files require special attention <!-- 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!} **Context used:** - Context from `dashboard` - CLAUDE.md ([source](https://app.greptile.com/review/custom-context?memory=fd949e91-5c3a-4ab5-90a1-cbe184fd6ce8)) - Context from `dashboard` - AGENTS.md ([source](https://app.greptile.com/review/custom-context?memory=0d0c8278-ef8e-4d6c-ab21-f5527e322f13)) <!-- /greptile_comment -->