Copy the approved MLS description in one tap from the listing, as plain text ready for the MLS #107

Intent: the agent's last step into the MLS is one tap, and only person-approved words can be copied.

Done looks like:

• [x] An approved MLS description shows a Copy for MLS button beside it, built like the social post's Copy post (#100): a button with JavaScript, a selectable read-only box without it.
• [x] What is copied is the approved text only: no property page link, no emoji, no HTML, line breaks kept as plain paragraphs.
• [x] An unapproved (draft) MLS description offers no copy control.
• [x] Tests: approved shows the control and the exact text; draft shows none; the no-JavaScript fallback holds the same text; bun scripts/design-lint.ts and the a11y test pass.

Files: src/pages/listing.ts, static/listing.js, a test beside the copy-post test, README.md one line. Risks: waits on the length meter because both change the same asset block in src/pages/listing.ts. Suggested crew: a builder.

Reviewed pull #114 at its head: ticked An approved MLS description shows a Copy for MLS button beside it, built like the social post's Copy post (#100): a button with JavaScript, a selectable read-only box without it.; What is copied is the approved text only: no property page link, no emoji, no HTML, line breaks kept as plain paragraphs.; An unapproved (draft) MLS description offers no copy control.; Tests: approved shows the control and the exact text; draft shows none; the no-JavaScript fallback holds the same text; bun scripts/design-lint.ts and the a11y test pass..