docs: Extract sequence documentation to dedicated SEQUENCE.md file

Moves comprehensive sequence system documentation out of demo.seq into
a proper documentation file, keeping the timeline file clean and focused.

Changes:
- New file: doc/SEQUENCE.md with complete .seq format reference
- Streamlined: assets/demo.seq reduced from 207 to 104 lines
- Updated: README.md to include SEQUENCE.md reference

Benefits:
- Easier to read and navigate the actual timeline
- Documentation separately viewable in markdown
- Better for version control (timeline vs doc changes separated)
- Follows project convention of dedicated doc files
- Makes demo.seq more approachable for quick edits

The timeline file is now 50% smaller while all documentation remains
easily accessible in the standard doc/ directory.

0 files changed, 0 insertions, 0 deletions