Add project: YYLO Ledger

[InsightFactoryAPP]

Summary

Adds YYLO Ledger to projects.yaml (+4 lines, single file):

  - name: YYLO Ledger
    github_id: yylo-dev/yylo-ledger
    category: others
    pypi_id: yylo-ledger

YYLO Ledger is a command-line, git-native task and workflow ledger for projects driven by coding agents: the Kanban board and task state are stored as hash-chained Markdown inside the repository, alongside receipts, archives, and typed merge/release flows across agent worktrees.

Why it fits

• Python package distributed on PyPI (pip install yylo-ledger), MIT-licensed, with daily development activity (last push 2026-09-02).
• The toolchain it belongs to shows real usage: the companion CLI is at 57★ with ~560 npm downloads/month (@yylo/cli). The ledger itself is the newest component (created 2026-08-17), so I've kept the entry minimal and factual — if it is still too new for the list, closing this is completely fine and I'll happily re-submit once it has more traction.
• Categorized as others following the pre-commit precedent, since a task/workflow ledger does not match any of the classic Python-tooling categories; happy to re-file or drop the explicit category if you prefer.

Validation

• python3 -c "import yaml; yaml.safe_load(open('projects.yaml'))" passes — 270 projects, names unique.
• Only projects.yaml is touched; the README is left to the weekly update.

Disclosure

I'm on the YYLO team, and this PR was prepared with an AI coding agent and reviewed by me. A sibling entry for the same project is also open on lukasmasuch/best-of-python (#323) — both lists have distinct scopes, but I'm flagging it for transparency.