chore: remove sync-upstream workflow, document local patch-based sync

DIVERGENCES.md

@@ -1,11 +1,12 @@
 # Divergences from upstream
 
-Every deliberate change to an upstream file is listed here. When a `sync-upstream` merge
-conflicts, this table tells you what the conflict is about and how to resolve it. If you
-edit an upstream file and it is not in this table, add it — an unlisted divergence is a bug.
+Every deliberate change to an upstream file is listed here. When an upstream sync patch
+(see README → Syncing with upstream) conflicts, this table tells you what the conflict is
+about and how to resolve it. If you edit an upstream file and it is not in this table,
+add it — an unlisted divergence is a bug.
 
-New files that upstream does not have (this file, `NOTICE`, `.github/workflows/sync-upstream.yml`,
-future `packages/codev-*`) never conflict and are not tracked here.
+New files that upstream does not have (this file, `NOTICE`, future `packages/codev-*`)
+never conflict and are not tracked here.
 
 ## Changed upstream files
 

README.md

@@ -40,20 +40,27 @@ Notes:
 
 ## Syncing with upstream
 
-A scheduled GitHub Action ([`sync-upstream.yml`](.github/workflows/sync-upstream.yml)) merges upstream `dev` into `main` weekly and opens a PR. It can also be run on demand (Actions → sync-upstream → Run workflow) against any upstream branch or tag.
-
-One-time repo setup for the action to open PRs: **Settings → Actions → General → Allow GitHub Actions to create and approve pull requests**.
-
-Manual sync:
+Syncing is manual and local — there is no CI workflow. `main` carries fork commits only
+(history was truncated; it shares no ancestry with upstream), so `git merge upstream/...`
+does not work. Instead, apply upstream's changes as a 3-way patch between release tags.
+The tag the fork is currently on is the `version` in `packages/opencode/package.json`.
 
 ```sh
-git fetch upstream --tags
+git fetch upstream --tags        # also brings in the blobs `git apply -3` needs
 git checkout -b sync-upstream main
-git merge upstream/dev
+# FROM = current version in packages/opencode/package.json; TO = target release
+git diff v<FROM> v<TO> --binary -- . ':(exclude)bun.lock' | git apply -3 --index
 # Conflicts in our own files: see DIVERGENCES.md for each file's resolution strategy.
-# Conflicts in bun.lock or generated code: regenerate (bun install / bun run generate), never hand-merge.
+# Files we deleted (locales, README translations): if the patch re-adds them, delete them again.
+bun install                      # regenerate bun.lock, never patch it
+bun turbo typecheck
+git commit -m "chore: sync upstream v<TO>"
 ```
 
+`git apply -3` leaves ordinary conflict markers where our divergences overlap upstream
+changes — the same conflict surface the old merge had. If a hunk fails outright, it is
+usually against a file we deleted or renamed; check DIVERGENCES.md before forcing it.
+
 ## Divergence policy
 
 Features go, in order of preference: