v1.0.1-20260909

Fix issues with Lete Sans Math fonts (upgraded to v0.63)

Release v1.0.0 on 20260903

Reorganise the notes into one public, single-template repository

Previously Part IA was a private repo whose root was dominated by the Ponder
tooling, while Part IB and the revision sheets were untracked, and the template
had been copied seventeen times with no two copies alike.

Structure
- One repository rooted at the notes tree, with slug directories
  (part-ia/groups/main.typ) and no spaces or en-dashes in any path.
- The Ponder tooling is a self-contained subproject in ponder/: its
  package.json, tsconfig and lockfile live there and it resolves the notes root
  as its own parent rather than the working directory.
- Compiled PDFs are no longer committed. CI builds every variant and attaches
  them to releases.

One template
- template/ replaces nine template.typ copies, seven html-template.typ copies
  and seven identical ponder.typ shims. The PDF and HTML flavours are one
  definition branching on the target, so the exporter no longer swaps one
  template file over another.
- Each course keeps its own notation in symbols.typ, re-exported by a two-line
  prelude.typ that chapters import instead of the template directly.
- Figure paths are root-absolute, because the shared template resolves read()
  against its own location rather than the caller's.

Four export targets
- theme=light|dark and font=sans|serif select the variant at compile time.
  Sans is Inter 4.1 with Lete Sans Math 0.62; serif is IBM Plex Serif 3.006
  with IBM Plex Math 1.000. Both suites are vendored under fonts/ and builds
  ignore system fonts, so any clone reproduces them.
- Verified: the light/sans build of Differential Equations, Dynamics and
  Relativity, Groups and Probability matches the pre-migration page count
  exactly, and the Groups HTML export is token-identical to the old one.

Fixes and hygiene
- Vectors and Matrices compiles again; its own template was missing
  dynamic-svg2, which chapter 4 uses.
- Dynamics and Relativity gets a doc id of its own, previously shared with
  Groups, and equation numbering as a template option.
- Removed absolute home paths from the metadata of 194 Inkscape figures,
  verified pixel-identical.
- Added a README, CC BY-NC-SA 4.0 for the notes, MIT for the code, and the
  Open Font Licence for every vendored family.