A repository's map draws what is open and counts what is done: trevato/forge's /map under 400 KB and 300 ms #6121

Measured on the forge on 2026-10-26: /trevato/forge/map takes 1.6–2.5 s on the server (map;dur≈2300) and sends 3.5 MB (527 KB gzipped), because it draws 1,934 done issues next to about 400 open ones. The owner steers from this page, and it is the slowest page on the forge.

Done when:

• [ ] By default the map lays out and draws only open issues (ready, waiting, working, blocked, held, parked, deferred). Done issues appear as one count in the counts line, linking to ?done=1, which draws everything as today.
• [ ] Ready now, Blocked on, the critical path and the pillar rows are unchanged, because they are already about open work.
• [ ] A test with 2,000 closed and 300 open issues asserts that the default page has no node for a closed issue, that ?done=1 has them, and that the body is under 400 KB.
• [ ] Server-Timing splits map into graph, layout, marks and pillars.

Files: src/web/pages/map.ts, test/map-page.test.ts. Risk: /og/map and the live region redraw the same graph, so keep them to the same default. The layout cache key must include the filter.

Replaced by #6174. Since this was written, main has split the map page's Server-Timing (#5785), and /og/map already draws only open issues. #6174 keeps what is left: the page draws open issues by default, and a separate padded "Show done" / "Open only" link sits beside a plain done N badge (sentinel's design ask). It also updates docs/PLANNING.md and adds the 2,000/300 test. Pull #6132's branch is the starting point.