fix(cli): read Notion page titles by property type instead of name

[tckaros]

Closes #1438

extract_page_title looked for titles using a list of conventional property
names (title, Title, Name, name, and Page).

Notion database entries can name their title property freely—for example,
Topic. The lookup therefore missed custom-named title properties and fell
back to the raw page ID for both the filename and frontmatter title.

The content still synced correctly, but the opaque filename made the document
difficult for agents to discover when listing files for relevant context.

Notion pages have a property of type title, so the lookup now identifies the
title by property type instead of name. Existing behavior is preserved for
regular pages, and empty titles still fall back to the page ID.

Testing

• Added unit tests covering:
  • a custom-named title property (Topic);
  • an empty title falling back to the page ID.
• Notion and sync CLI test suites pass (111 tests).
• Tested against a real Notion workspace: a database entry now syncs as
  ai-agents-karos-basic-knowledge-3ae5f0e8.md, with its actual title in the
  frontmatter, instead of 3ae5f0e8…-3ae5f0e8.md.

🤖 Generated with Claude Code

[cubic-dev-ai]

No issues found across 2 files

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