[Docs](feat) Add Ascend extension API auto-render docs

[Misaka19280hw]

Why

Complete the public Chinese Python API reference for the Ascend extension APIs assigned in this documentation batch. These pages use the repository's automatic rendering path instead of adding standalone Markdown pages.

What

• Add auto-render constraints and matching examples for CORE, MODE, PIPE, IteratorType, SYNC_HINT, EVENT_ID, SyncEventSlot, custom, register_custom_op, and sub_vec_num.
• Add the missing SYNC_HINT, EVENT_ID, and SyncEventSlot entries to the extension API RST index.
• Add lightweight documentation-build stubs for the public SYNC_HINT and EVENT_ID aliases.
• Keep the existing sub_vec_id and sync_block_all/set/wait entries and examples unchanged.

Validation

• pre-commit run --from-ref origin/main --to-ref HEAD
• git diff origin/main..HEAD --check
• Verified all 14 assigned public APIs have a constraint entry, a same-named example, and exactly one RST entry.
• Verified the forced documentation Mock path resolves all newly documented symbols.
• Verified all added Python examples parse successfully.
• Full Sphinx rendering was not run locally because Sphinx/docutils are not installed; the repository documentation checks should provide the integration result.

New contributor declaration

• I am not making a trivial change, such as fixing a typo in a comment.
• I have written a PR description following these rules.
• I have run pre-commit run --from-ref origin/main --to-ref HEAD.
• This PR does not need a runtime test because it only changes documentation metadata, examples, and documentation-build mocks.
• I have not added any lit tests.