Start the rebuild: note schema, vault kit and data migration

Phase 1 of the functional design plan.

- Move the old site into legacy/, unchanged, for reference. It still
  builds from there until cutover.
- Add packages/schema: the one definition of all 20 note types, with
  field titles and descriptions, note and vault checks, and JSON Schema
  export so later editing tools and the MCP server share it.
- Add vault-kit: Obsidian templates generated from the schema, and the
  Site guide for 24.01_PersonalWebsite.
- Add tools/migrate: turns the legacy JSON, collections, store data and
  page text into 545 Site folder notes and 84 images, and checks the
  result with the schema.

Co-Authored-By: Claude Opus 5.5 (1M context) <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_012aSbo2D1qP8cMFQCykf7kx

vault-kit/24.01_PersonalWebsite/Site/_templates/Post.md

@@ -0,0 +1,17 @@
+---
+type: "post"
+title: "{{title}}"
+publish: false  # Only notes set to true appear on the site.
+created: "{{date:YYYY-MM-DD}}"  # optional
+date: "{{date:YYYY-MM-DD}}"
+topic:  # one of: Making, Tabletop, Library, Work and tech, Life
+postType: "article"  # optional. one of: article, build log, case study
+summary:  # One or two sentences for lists and link previews.
+pinned: false  # optional. Takes the top slot on the Blog.
+employer:  # optional. Case studies only. Leave out for personal projects.
+role:  # optional. Case studies only.
+period:  # optional. Case studies only, like 2021 to now.
+tech: []  # optional
+---
+
+<!-- The post itself. -->