docs: provide current paired SDK source installation

[anycodes]

Description

Both current0.3.0 package metadata endpoints return404, while root/package READMEs and active guides still instructed index-only installs. Add one bilingual paired-source installation guide, update current install/extras/examples/CLI cross-links, and replace the retired root version command with actual distribution metadata inspection. Remove unavailable PyPI badges/publication wording. Preserve package names, same-version namespace coupling, historical design/evidence and runtime source.

The known tested immutable source is accepted native e86cb0b; the guide explicitly distinguishes it from a current development checkout. Move actually merged config-composition PR61's decision/index to implemented (mergef701b26 after9/9).

Type of Change

• Documentation

Testing

• Fresh isolated public server+client[all] source install,pip check and real SDK/server/MCP/orjson/yaml/filelock imports/matching0.3.0 version inspection all exit0.
• Independent base pair source installation already passed; fresh PyPI metadata returns404 for both names.
• Health106PASS/1existingWARN/0FAIL,hygiene/whitespace and manual bilingual index/table/diff review pass.
• Latest required hosted matrix pending (draft until complete).

Checklist / Definition of Done

• Bilingual current docs/indexes/changelog and owner note/evidence.
• Actual installation behavior verified; no redundant prose-only tests.
• Runtime source/exports/schema/dependencies and historical evidence unchanged.
• Prior accepted runtime cloud116PASS remains historical support; this prose-only change performs no cloud mutations or unrelated model tests.
• Required hosted acceptance.

No package release,naming change or provider/model acceptance is claimed. Consumer install recipes already use this same source; website/registry hosted403 remains separate.