Wire real OpenCode selectors and URLs from captured pages

Go page (/workspace/{id}/go): parse three [data-slot=usage-item] frames
(Rolling/Weekly/Monthly) into usage percentages + computed resets_at from the
relative reset-duration text. Zen page (/workspace/{id}): parse
[data-slot=balance] b into remaining + currency unit. Add an offline unit test
against tmp/ captures. Fix pretty renderer (percent display, money format,
day-aware relative times). Update DESIGN.md, README, examples and config
template to the real wrk_ workspace ids.

examples/ocd.toml

@@ -6,10 +6,10 @@ default_ttl_secs    = 180
 [[account]]
 name              = "work"
 cookie            = "${OCD_COOKIE_WORK}"
-default_workspace = "ws_REPLACE_ME"
+default_workspace = "wrk_REPLACE_ME"
 extra_workspaces  = []
 
 [[account]]
 name              = "personal"
 cookie            = "ocd_session=...."
-default_workspace = "ws_REPLACE_ME"
+default_workspace = "wrk_REPLACE_ME"