Trim tool schemas, add param aliases, new PR methods (#191)

- Tool list size reduced by 26.6% (43,032 → 31,599 bytes on the `tools/list` JSON-RPC response).
- Trim redundant tool/param descriptions; shared description constants for `owner`/`repo`/`page`/`per_page`.
- Schemas now use github-mcp-server param names directly: `issue_number` (was `index` on issue tools), `pull_number` (was `index` on PR tools), `path` (was `filePath`), `query` (was `keyword` on user/repo search), `per_page` (was `perPage`).
- New PR read methods `get_files` and `get_status`; new PR write method `update_branch` (update PR branch from base).
- `list_org_repos` now uses `per_page` (was `pageSize`).
- `milestone_write` accepts `update` and `edit`.
- `create_branch` `old_branch` is optional; Gitea defaults to the repo default branch.
- Fix `list_commits` handler to honour optional `page`/`per_page` schema (was erroring out when callers omitted them).

---
This PR was written with the help of Claude Opus 4.7

Reviewed-on: https://gitea.com/gitea/gitea-mcp/pulls/191
Reviewed-by: Lunny Xiao <xiaolunwen@gmail.com>
Co-authored-by: silverwind <me@silverwind.io>
Co-committed-by: silverwind <me@silverwind.io>

pkg/params/params_test.go

@@ -5,6 +5,17 @@ import (
 	"testing"
 )
 
+func TestGetPagination(t *testing.T) {
+	page, perPage := GetPagination(map[string]any{"page": float64(2), "per_page": float64(40)}, 30)
+	if page != 2 || perPage != 40 {
+		t.Errorf("GetPagination = (%d, %d), want (2, 40)", page, perPage)
+	}
+	page, perPage = GetPagination(map[string]any{}, 30)
+	if page != 1 || perPage != 30 {
+		t.Errorf("GetPagination defaults = (%d, %d), want (1, 30)", page, perPage)
+	}
+}
+
 func TestToInt64(t *testing.T) {
 	tests := []struct {
 		name string