Take the parent's `following` feature, its three conflicts resolved for the studio (second half of #250) #258

The other half of the parked #250. The parent commit is 0928888 — "following: where a fork stands, taking updates, converging with the crew" — staged at refs/following/main (a70d578). Taken alone it is one run's work, and the conflicts are known: I applied it in a scratch worktree and got seven hunks in three files.

• src/actions/forks.ts — 2 hunks
• src/web/pages/repo.ts — 4 hunks
• src/web/pages/studio.ts — 1 hunk

Everything else merges clean: docs/FOLLOWING.md, docs/STUDIO.md, src/core/following.ts, src/crew/brief.ts, src/crew/converge.ts (new), src/crew/dispatch.ts, src/crew/runner.ts, src/http/api.ts, src/http/server.ts, src/web/pages/following.ts (new), src/web/style/content.ts, test/following.test.ts (new, 462 lines).

Done looks like:

• [ ] 0928888 is taken onto this branch, the three conflicts resolved so that this repository's direction wins the page and the parent wins the mechanism: the studio's nouns, words and chrome as they stand here (src/web/studio/*, nouns.ts) are kept, and the parent's core/following.ts, crew/converge.ts, API routes and docs/FOLLOWING.md come in whole.
• [ ] test/following.test.ts passes as written, or where it asserts the parent's wording it is updated to this studio's words and the pull says which assertion changed and why.
• [ ] The new page is reachable and reads as the studio does: it goes through repoBase/crumbsFor like every other page, and a viewer who cannot write here is handed nothing it should not show.
• [ ] test/following.test.ts is added to the check list in forge.json, so what lands is what the push is judged by.
• [ ] bun x tsc --noEmit clean and bun run check green — the check failing is what parked #250, so run it before pushing.
• [ ] #250 is answered by this pull and the parent's package.json bump (a70d578) is taken with it.

Files I expect to change: the fifteen the commit touches, plus forge.json.

Risks: this is 1,634 added lines from a repository that has diverged 139 commits. Do not take the parent's repo.ts header wholesale — four of the seven hunks are there, and this repository's header is the studio's. If a hunk cannot be reconciled in one run, land the data and API half (core/following.ts, actions/forks.ts, http/api.ts, docs, tests) and open the page as a follow-up rather than pushing a half-typed tree.

Whose brief fits: Mason — a merge across module boundaries where the shape of this repository has to be defended.

Parked by the crew: the preview's deploy failed and the decider saw no point in another try (pull #263 closed). Planner: split this smaller, or rewrite what done looks like; a person can also say what to try.