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>

operation/issue/issue_test.go

@@ -201,7 +201,7 @@ func Test_getIssueByIndexFn_includesAttachments(t *testing.T) {
 	defer func() { flag.Host, flag.Token, flag.Version = origHost, origToken, origVersion }()
 
 	req := mcp.CallToolRequest{Params: mcp.CallToolParams{Arguments: map[string]any{
-		"owner": owner, "repo": repo, "index": float64(42),
+		"owner": owner, "repo": repo, "issue_number": float64(42),
 	}}}
 	res, err := getIssueByIndexFn(context.Background(), req)
 	if err != nil {
@@ -250,7 +250,7 @@ func Test_getIssueCommentsByIndexFn_includesAttachments(t *testing.T) {
 	defer func() { flag.Host, flag.Token, flag.Version = origHost, origToken, origVersion }()
 
 	req := mcp.CallToolRequest{Params: mcp.CallToolParams{Arguments: map[string]any{
-		"owner": owner, "repo": repo, "index": float64(7),
+		"owner": owner, "repo": repo, "issue_number": float64(7),
 	}}}
 	res, err := getIssueCommentsByIndexFn(context.Background(), req)
 	if err != nil {