Copy an approved social post, with its property page link, in one tap from the listing #100

Each approved social post on a listing now has a Copy post button, and a draft has none. The new tests and the walkthrough, a11y, listings, hostile and design suites pass. I ran those, not the whole suite; the forge runs the full check on the push. I didn't open the preview or tap the button in a browser.

• What it copies: the approved words, then the listing's absolute property page URL (/homes/:id). If the words already carry that link, as the open house reminder does, it isn't added twice.
• Without JavaScript: the page shows a "Copy post" disclosure holding a selectable read-only textarea with the same text.
• With JavaScript: a few lines in static/listing.js show the button, hide the textarea fallback, copy with navigator.clipboard, and say "Copied the … with its link" in the existing aria-live region. Clipboard needs https, which production has.
• Where: src/pages/listing.ts has the new copyPost and postCopy, and editor now takes the request origin. There is no inline script, and the CSP and contract are untouched. The README walkthrough has a "Copy a post" paragraph.
• Tests: src/copy.test.ts checks that a draft has no copy block, an approved post shows its words plus the absolute link, hostile words stay escaped (<script>), and the page has no inline script.
• One fix on the way: the a11y suite requires an aria-label to start with the visible text, so the button's label begins "Copy post: …".

I added no new CSS classes.

Not run here:

• Type check: bun x tsc --noEmit can't run, because the repo has no tsconfig.json.
• Gate and fast scripts: scripts/gate.ts and scripts/fast.ts don't exist.
• Design lint: the script here is scripts/lint-design.ts, not design-lint.ts. I ran it and it printed no violations.

Closes #96

Each approved social post on a listing now has a Copy post button, and a draft has none. The new tests and the walkthrough, a11y, listings, hostile and design suites pass. I ran those, not the whole suite; the forge runs the full check on the push. I didn't open the preview or tap the button in a browser.

• What it copies: the approved words, then the listing's absolute property page URL (/homes/:id). If the words already carry that link, as the open house reminder does, it isn't added twice.
• Without JavaScript: the page shows a "Copy post" disclosure holding a selectable read-only textarea with the same text.
• With JavaScript: a few lines in static/listing.js show the button, hide the textarea fallback, copy with navigator.clipboard, and say "Copied the … with its link" in the existing aria-live region. Clipboard needs https, which production has.
• Where: src/pages/listing.ts has the new copyPost and postCopy, and editor now takes the request origin. There is no inline script, and the CSP and contract are untouched. The README walkthrough has a "Copy a post" paragraph.
• Tests: src/copy.test.ts checks that a draft has no copy block, an approved post shows its words plus the absolute link, hostile words stay escaped (<script>), and the page has no inline script.
• One fix on the way: the a11y suite requires an aria-label to start with the visible text, so the button's label begins "Copy post: …".

I added no new CSS classes.

Not run here:

• Type check: bun x tsc --noEmit can't run, because the repo has no tsconfig.json.
• Gate and fast scripts: scripts/gate.ts and scripts/fast.ts don't exist.
• Design lint: the script here is scripts/lint-design.ts, not design-lint.ts. I ran it and it printed no violations.