docs(readme): move the agent capability matrix under Quick Start

[jeff-r2026]

Summary

• Move the agent capability matrix from docs/product-overview onto the README, directly after Quick Start, as Product Overview.
• Add a one-line Git framing plus short Team Execution / Context / Improvement blurbs, and a closing note that teammates get the team's AI assets as soon as they open an agent.
• Keep the five README locales in sync; the product overview docs now point back to the README instead of duplicating the table.

Test plan

• Open README.md and README.zh-CN.md on GitHub: Quick Start examples, the join/open-agent line, then the Product Overview bullets and matrix.
• Confirm ja / ko / th READMEs have the same section order and translated copy.
• Click through from docs/product-overview.md and docs/product-overview.zh-CN.md to the README Product Overview heading.
• Scan the matrix rows against the previous product-overview table (no missing agents; Pi footnote removed on purpose).

Made with Cursor

[github-actions]

Code Erosion Report

Informational — never blocks the merge. scb-check==0.2.0 SlopCodeBench metrics; method & caveats in docs/ci-code-erosion.md.

Metric	Value	Human band	Agent band	Reading
Verbosity*	0.087	0.15	0.33	human
Erosion	0.655	0.31	0.68	agent
Cognitive erosion	0.855	–	–	–

Scanned 260 files / 43450 SLOC · high-CC functions 250/3033

* On TypeScript, verbosity is partial and the bands are Python-calibrated.

Rule hits (TS verbosity layer)

Standalone ast-grep, separate from the number above.

Rule	Hits
unnecessary-else-after-return	23
empty-catch-block	6
redundant-ternary-same	1

30 distinct lines flagged across src/.