Document diffusion area ownership for runtime, optimization, and docs based on maintainer team alignment. Update committer area descriptions for @RuixiangMa, @wtomin, @ZJY0516, and @yuanheng-zhao. Signed-off-by: hsliuustc0106 <liuhongsheng4@huawei.com> Co-authored-by: Cursor <cursoragent@cursor.com>