feat: open a group, a folder or a file from a #/name@owner link

A group can now be reached by the handle shown under its name, and a path
after it points inside the group: #/name@owner/root/dir/file downloads the
file and opens Files on its folder; a folder opens Files there. The handle
is resolved in the client against the account's own /v1/groups/mine, so no
hub route answers for a name and nobody can probe for one. While a group is
open the address shows the handle (replace, no history entry); a linked path
is taken out of the address once acted on, so a reload does not download
twice.

Signing in no longer sends everyone home: the form stood in for the page the
address named, and that is where a link opened signed out was going.

group-link.js holds the parsing and lookups, executed whole by
test_group_link.py; harness/group_link_probe.py drives the router in Chrome.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

0 files changed, 0 insertions, 0 deletions