feat(webui): read-only workflow policy & guardrail visibility (Closes #646)

Phase 3 child of the Web Console epic #631. Operators can now see the active
workflow policy/guardrail configuration from the console instead of reading the
repo tree.

- webui/policy_inventory.py (new): redacted, machine-readable guardrail
  inventory. One row per major guardrail (role separation/RBAC, lease rules,
  worktree binding, merge confirmation, redaction, contamination, allocator
  policy, audit logging, mutation gating) with source pointers (file/module/doc)
  and a compact active projection from the existing safe policy accessors.
  Fail-soft per entry; whole payload run through console_redaction before emit;
  diff vs documented default where feasible.
- webui/policy_views.py (new): HTML cards with source pointers, active config,
  and the documented-default diff; read-only page copy, no forms.
- webui/app.py: register GET /policy and GET /api/v1/policy (additive).
- webui/layout.py: add Policy nav item.
- tests/test_webui_policy_visibility.py (new): guardrail presence + source
  pointers (AC1), redaction incl. planted-secret masking and scan_for_secrets
  (AC2/AC3), read-only page + no-mutation routes (AC4), fail-soft rendering.
- docs/webui-local-dev.md: route table + read-only policy-visibility section.

Read-only throughout; no policy editing, no gate-weakening toggle, secrets
redacted.

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

webui/policy_views.py

@@ -0,0 +1,104 @@
+"""HTML views for the workflow policy and guardrail inventory (#646)."""
+
+from __future__ import annotations
+
+import html
+import json
+
+from webui.policy_inventory import PolicyEntry, PolicyInventorySnapshot
+
+
+def _source_pointer(source) -> str:
+    path = source.path
+    if source.anchor:
+        path = f"{path}#{source.anchor}"
+    return (
+        f"<li>{html.escape(source.label)} — "
+        f"<code>{html.escape(path)}</code> "
+        f"<span class='muted'>({html.escape(source.kind)})</span></li>"
+    )
+
+
+def _active_block(entry: PolicyEntry) -> str:
+    if entry.error:
+        return (
+            "<p class='muted'><strong>Active value unavailable:</strong> "
+            f"{html.escape(entry.error)}</p>"
+        )
+    if not entry.active:
+        return "<p class='muted'>No live projection for this guardrail.</p>"
+    pretty = json.dumps(entry.active, indent=2, sort_keys=True, default=str)
+    return f"<pre class='prompt-text'>{html.escape(pretty)}</pre>"
+
+
+def _diff_block(entry: PolicyEntry) -> str:
+    if entry.diff is None:
+        if entry.documented_default is None:
+            return "<p class='muted'>Diff vs documented default: not feasible (no declared default).</p>"
+        return "<p class='muted'>Diff vs documented default: unavailable.</p>"
+    status = entry.diff.get("status", "unknown")
+    badge = "badge-claimed" if status == "matches_documented_default" else "badge-blocked"
+    rows = []
+    for key, cell in (entry.diff.get("checked") or {}).items():
+        marker = "✓" if cell.get("matches") else "✗"
+        rows.append(
+            "<tr>"
+            f"<td><code>{html.escape(str(key))}</code></td>"
+            f"<td><code>{html.escape(str(cell.get('expected')))}</code></td>"
+            f"<td><code>{html.escape(str(cell.get('observed')))}</code></td>"
+            f"<td>{marker}</td>"
+            "</tr>"
+        )
+    table = ""
+    if rows:
+        table = (
+            "<table class='detail'><thead><tr>"
+            "<th>Key</th><th>Documented</th><th>Active</th><th>Match</th>"
+            "</tr></thead><tbody>"
+            f"{''.join(rows)}</tbody></table>"
+        )
+    return (
+        f"<p class='meta'>Diff vs documented default: "
+        f"<span class='badge {badge}'>{html.escape(status)}</span></p>"
+        f"{table}"
+    )
+
+
+def _entry_card(entry: PolicyEntry) -> str:
+    sources = "".join(_source_pointer(s) for s in entry.sources)
+    return (
+        "<div class='prompt-card'>"
+        f"<h3>{html.escape(entry.title)} "
+        f"<span class='badge'>{html.escape(entry.category)}</span></h3>"
+        f"<p>{html.escape(entry.summary)}</p>"
+        "<p class='meta'><strong>Source pointers</strong></p>"
+        f"<ul>{sources}</ul>"
+        "<p class='meta'><strong>Active configuration</strong></p>"
+        f"{_active_block(entry)}"
+        f"{_diff_block(entry)}"
+        "</div>"
+    )
+
+
+def render_policy_page(snapshot: PolicyInventorySnapshot) -> str:
+    categories = ", ".join(html.escape(c) for c in snapshot.categories) or "none"
+    cards = "".join(_entry_card(e) for e in snapshot.entries)
+    build_errors = ""
+    if snapshot.build_errors:
+        items = "".join(
+            f"<li>{html.escape(err)}</li>" for err in snapshot.build_errors
+        )
+        build_errors = (
+            "<div class='stub'><p><strong>Some guardrails could not be built:"
+            f"</strong></p><ul>{items}</ul></div>"
+        )
+    return (
+        "<h2>Workflow policy &amp; guardrails</h2>"
+        f"<p class='muted'>{html.escape(snapshot.note)}</p>"
+        f"<p class='meta'>Schema v{snapshot.schema_version} · "
+        f"{len(snapshot.entries)} guardrails · categories: {categories}</p>"
+        f"{build_errors}"
+        f"{cards}"
+        "<p class='muted'>This page is read-only. It reports enforced policy "
+        "and never edits or weakens a gate. Secret values are redacted.</p>"
+    )