add send patch panel

docs/TODO.md

@@ -17,6 +17,11 @@
   - [x] Patch is generated from the checkout at submit time (`format_patch_between` on the stored merge base); panel closes after publishing, errors surface in the PR list banner.
 - [x] Removed with the dialog: paste textarea, draft checkbox, branch-name input and the mirror-clone apply-check hint (store behavior unchanged: `open_pull_request` still publishes the series + `branch-name`/`merge-base`/`r` tags and pushes the tip).
 
+### Send patch panel (classic paste flow)
+
+- [x] "Send patch" entry in the repo header PRs dropdown (`RepoAction::SendPatch`) and a "New pull request ▾ Send patch" dropdown replacing the PR list's plain new-PR button.
+- [x] `send_patch.rs` center panel: title + optional description + `git format-patch` paste area; submits through `RepoStore::open_pull_request` (no checkout, no `branch-name`/`merge-base`). Synchronous store errors (malformed/oversized patch, sign-in) keep the panel open with an inline error; the panel closes once the publish is underway.
+
 - [x] P1: `branch-name` tag + `r` EUC tag on PR creation; draft checkbox in the new-PR dialog (dialog since replaced by the panel above).
 - [x] P1: `RepoStore::update_pull_request` (kind 1619 + root-revision patch) with an author-only "Update" button on the PR detail header.
 - [x] P1: `latest_update` filters by PR author.