Slice 10: create_pr (open a pull request)

forge CreatePullRequest (Gitea; empty base resolves to the repo default branch). Service CreatePR records a pr-created event. HTTP POST /api/repo/pr/create; MCP tool create_pr; <pr-list> New pull request button (head = selected repo current branch, base = default). Live-tested end-to-end: app create_pr opened a real PR (base auto-resolved), listed, then cleaned up; main untouched.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

CHANGELOG.md

@@ -230,3 +230,16 @@ Append-only running history of all changes (AGENT.md §9.1). Newest last.
   `cmd/server/main.go`, `components/repo-menu`, `web/templates/help.html`,
   `AGENT.md` (§8.1). Checkout isn't §1.4-destructive — git refuses if it would
   overwrite uncommitted changes.
+
+## 2026-09-20 — Slice 10: create_pr
+- **What:** forge `CreatePullRequest` (Gitea; empty base → repo default branch,
+  via GetRepo). Service `CreatePR` (records `pr-created`). HTTP
+  `POST /api/repo/pr/create`. MCP tool `create_pr`. `<pr-list>` gained a
+  "New pull request…" button (head = selected repo's current branch, base =
+  default). AGENT.md §8.1 lists `create_pr` in Act.
+- **Why:** Open PRs from the app or Claude — the front half of the PR workflow
+  whose back half is "Merge & clean up".
+- **Affects:** `internal/forge`, `internal/service`, `internal/mcp`,
+  `cmd/server/main.go`, `components/pr-list`, `web/templates/help.html`,
+  `AGENT.md`.
+- **Note:** the head branch must already exist on the remote (push first).