v0.2.0 — import fix + comments CRUD

Fixes

• Import/export was returning empty pages. Notion quietly added an extra .value wrapper in recordMap entries, so every tool that read blocks silently parsed nothing. Unwrapped in one place via a new normalizeBlockMap() + unwrapRecord() helper.
• notion_export_page now throws a real error on unknown / inaccessible pages instead of returning "".
• Optional NOTION_DEBUG=1 env var logs raw request/response to stderr for troubleshooting (stdout stays clean for JSON-RPC).

New features

• notion_list_comments — list open discussion threads on a page, including anchor context, author, and timestamps.
• notion_add_comment — start a new discussion. Pass anchor_text for an inline comment (yellow-highlighted on the matching text span, preserves existing bold/italic/code on that span); omit it for a block-level comment.
• notion_reply_comment — reply to an existing thread.

Other

• Fixed stale table unit test to match the native-table shape from 0.1.8.
• 77 unit + integration tests passing.