* feat(app): preview HTML files in the file pane
Renders .html/.htm files as a page in the file pane, with the same
Preview/Source toggle Markdown already has. The main use is reading
richer visual plans an agent wrote as a self-contained HTML page.
A preview is a viewer, not a browser. Each document is prefixed with a
doctype and a strict policy, so the policy is always the first element
and always lands in the parser-created head: inline script and style
run, and remote subresources, fetch, XHR, WebSocket, beacon, and form
posts are refused. The frame has an opaque origin, so it cannot reach
the app's DOM and storage and cookie APIs throw inside it.
One gap is left on web and cannot be closed there: a sandboxed
document may navigate itself, and no CSP directive in current browsers
prevents it -- navigate-to was dropped from CSP3 and is unenforced, and
meta refresh needs no script (both verified against the Chromium the
app ships against). The opaque origin bounds it to the page's own
contents, and SECURITY.md documents it. Native narrows it further by
refusing navigation after the initial document, with the caveat that
the decision runs in app JS.
Self-contained pages only -- a page that pulls a CDN script renders
unstyled, and Source still shows everything.
* fix(app): harden HTML preview behavior and tests
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Co-authored-by: Nicholas Salgueiro <nicholas.salgueiro@britecore.com>
Co-authored-by: Mohamed Boudra <boudra.moha@gmail.com>
