feat: add canonical workflow prompt library to web UI (Closes #428)

Expose short copy/paste operator prompts on /prompts derived from canonical
workflow files with workflow path and SHA-256 hash. Adds JSON export at
/api/prompts, copy buttons, and tests.

Co-Authored-By: Claude Opus 4.8 (1M context) <[email protected]>

webui/prompt_views.py

@@ -0,0 +1,80 @@
+"""HTML views for the prompt library (#428)."""
+
+from __future__ import annotations
+
+import html
+
+from webui.prompt_library import PromptEntry, load_prompt_library
+
+
+def _escape(text: str) -> str:
+    return html.escape(text, quote=True)
+
+
+def render_prompts_page() -> str:
+    entries = load_prompt_library()
+    cards: list[str] = []
+    for entry in entries:
+        cards.append(_render_prompt_card(entry))
+    body = (
+        "<h2>Prompt library</h2>"
+        "<p>Short copy/paste task prompts derived from canonical workflows. "
+        "Full policy remains in the cited workflow files — not duplicated here.</p>"
+        f"{''.join(cards)}"
+        f"{PROMPT_PAGE_SCRIPT}"
+    )
+    from webui.layout import render_page
+
+    return render_page(title="Prompts", body_html=body)
+
+
+def _render_prompt_card(entry: PromptEntry) -> str:
+    hash_short = (
+        f"<code>{_escape(entry.workflow_hash[:12])}</code>"
+        if entry.workflow_hash
+        else "<span class=\"muted\">n/a</span>"
+    )
+    task_mode = (
+        f"<code>{_escape(entry.task_mode)}</code>"
+        if entry.task_mode
+        else "<span class=\"muted\">n/a</span>"
+    )
+    note = (
+        f'<p class="meta">{_escape(entry.source_note)}</p>'
+        if entry.source_note
+        else ""
+    )
+    prompt_id = f"prompt-{entry.slug}"
+    return (
+        f'<section class="prompt-card" id="{_escape(entry.slug)}">'
+        f"<h3>{_escape(entry.label)}</h3>"
+        f'<p class="meta">Workflow: <code>{_escape(entry.workflow_path)}</code> · '
+        f"task_mode: {task_mode} · sha256: {hash_short}</p>"
+        f'<pre class="prompt-text" id="{prompt_id}">{_escape(entry.prompt_text)}</pre>'
+        f'<button type="button" class="copy-btn" data-copy-target="{prompt_id}">'
+        "Copy prompt</button>"
+        f"{note}"
+        "</section>"
+    )
+
+
+PROMPT_PAGE_SCRIPT = """
+<script>
+document.querySelectorAll('.copy-btn').forEach((btn) => {
+  btn.addEventListener('click', async () => {
+    const targetId = btn.getAttribute('data-copy-target');
+    const node = document.getElementById(targetId);
+    if (!node) return;
+    const text = node.textContent || '';
+    try {
+      await navigator.clipboard.writeText(text);
+      const prior = btn.textContent;
+      btn.textContent = 'Copied';
+      setTimeout(() => { btn.textContent = prior; }, 1200);
+    } catch (_err) {
+      btn.textContent = 'Copy failed';
+    }
+  });
+});
+</script>
+"""