docs: reposition project README

[cablate]

Why

The README still presented the project as a feature catalog. New visitors saw badges, tool counts, and a competitor table before understanding why agent location work needs more than a raw API.

What changed

• open with the orchestration problem this project solves
• explain observable outcomes and adoption reasons before implementation details
• present Plugin, CLI, stdio, and HTTP as equal integration choices
• group the 18 tools by user outcome instead of leading with a long inventory
• remove the stale competitor matrix and roadmap-heavy framing
• keep prerequisites, billing, attribution, safety, and credential limits near the decisions they affect
• fully align the English and Traditional Chinese reader paths
• update GitHub About description, homepage, and repository topics

Validation

• Skill validator passed
• unit tests: 36 passed
• smoke tests: 114 passed
• build passed
• npm pack dry run passed
• local Markdown links passed