v0.3.1 — maintenance and repositioning

The library is no longer presented as a trading library, and a confidential
name is gone from the entire git history.

Repositioning. 26 of the 42 prompts are non-trading, across eight areas,
and the audience is anyone wiring an agent into a codebase. The README, the
site nav, and the site front page all led with financial trading instead. A
42-prompt library was reading as a 16-prompt one.

• README leads with the count, the eight areas, and the agent-tool audience
• Nav leads with architecture and application; Financial Engineering moves last
• New framing: these are system prompts, not user prompts; how to pick one by
  mode; how to compose several for multi-area work

The financial prompts are unchanged and remain the depth differentiator.

History rewrite. A project name was in 2,016 file instances across 4
commits, 3 commit messages, and one filename. All rewritten; verified zero
occurrences across every commit, message, path, and tag. The four release
notes were already clean.

Corrections. Mode table said 30/7 against an actual 32/8. The browse
section said 38 prompts, wrong in every release since 0.1.0. Repository
description carried the old 38-prompt split.

Full detail in CHANGELOG.md.