docs: improve project SEO metadata

[Drswith]

Summary

Improve Quantex search discoverability without expanding product scope:

• add npm keywords and tighten the package description
• refine the English and Simplified Chinese README opening copy with natural lifecycle/AI coding assistant CLI terms
• add an OpenSpec product-readme delta for future package metadata and README discoverability edits

Linked Artifacts

• Issue:
• ADR:
• OpenSpec: openspec/changes/improve-project-seo
• Discussion:

Validation

• bun run memory:check
• bun run lint
• bun run format:check
• bun run typecheck
• bun run test (if behavior changed)
• Not run, explained below

bun run test was not run because this change only updates package metadata, product README wording, and OpenSpec documentation. No CLI behavior, structured output, schema, install/update logic, or executable code changed.

Additional validation:

• bun run openspec:validate
• bun run openspec:status -- --change improve-project-seo

Release Intent

• Release: not applicable - docs/process/test-only change

Docs Updated

• Not needed
• docs/...
• openspec/...
• Follow-up issue or OpenSpec change created instead

Scope Check

• I did not add a new ad hoc root-level Markdown file.
• I updated the relevant issue, ADR, spec, runbook, or captured the missing doc work as follow-up.
• I did not silently expand project scope without recording it explicitly.

Closure Check

• Working tree was clean after commit.
• Branch was pushed and this PR is the active delivery artifact.
• OpenSpec change is not needed, still active by design until merge, already archived, or queued for agent-driven archive closure.
• Release is not applicable, delegated to release automation, or verified.

Notes

The OpenSpec change remains active by design until this implementation PR merges; archive closure should be handled by the normal agent-driven follow-up.