Add click-to-copy to the URL/link tile used across the UI

[joestump-agent]

Context

The link "tile" that shows a URL's domain with a link glyph appears throughout the UI, but there's no way to copy the underlying URL — you can only click through to open it. We should add a small click-to-copy icon + behavior so the URL can be grabbed without navigating.

This is the same component shown in a message transcript (the github.com chip under a link) and on the Media → Links tab.

Where it renders

• Transcript link pill — internal/web/templates/partials.html (the msg-links block):

  <a class="link-pill" href="{{.URL}}" target="_blank" rel="noopener noreferrer nofollow">{{template "icon-link" $}}<span>{{.Domain}}</span></a>

• Media → Links tab — internal/web/templates/gallery.html:

  <a class="media-link-url" href="{{.URL}}" target="_blank" rel="noopener noreferrer nofollow">{{.URL}}</a>

Proposed solution

Reuse the existing copy affordance so there's no new JS or CSP change:

• internal/web/static/copy.js already powers copy buttons via data-copy-target + a .copy-btn with a copy→check icon swap (see the MCP blocks in internal/web/templates/settings.html). It reads the target element's text.
• Add a small .copy-btn (icon-only, icon-copy) beside the link tile that copies the full URL. Because copy.js copies the target element's text, either point it at an element holding the full {{.URL}} or extend copy.js to accept a data-copy-value attribute for cases where the visible text is just the domain (the transcript pill shows {{.Domain}}, not the full URL).

Acceptance criteria

• A copy icon appears on the link tile (transcript pill + Media Links row), keyboard-operable with an aria-label (e.g. "Copy link").
• Clicking it copies the full URL to the clipboard (not just the domain), with the existing copy→check confirmation and the #copy-announce aria-live announcement.
• No inline JS / no CSP change (reuse copy.js; script-src 'self').
• Works in both light and dark themes and doesn't break the tile's click-through-to-open behavior.

[joestump-agent]

Resolved by #19 (merged): both link-tile surfaces (transcript pill and Media → Links) now carry an icon-only copy button that copies the full URL via the new data-copy-value path in copy.js, with the shared #copy-announce live region moved into the persistent page shell. No CSP change. Minor follow-up noted in review: the buttons share an identical aria-label="Copy link"; a per-row label (e.g. "Copy link to {domain}") would help screen-reader navigation.

---

Generated by Claude Code