Update README/composer.json/CHANGELOG v1.0 wording

[nficano]

Three places carry stale v1.0 wording:

• README.md:4 — links to RFC-0001-v2.md (v1.0); update to spec/docs/draft-arcp-02.1.md
• composer.json:3 — description says "v1.0"; update to v1.1
• CHANGELOG.md:42 — "ARCP protocol v1.0"; update or contextualize

Verify: grep -rEn 'v1\.0|draft-arcp-02\.md([^.]|$)' README.md composer.json CHANGELOG.md docs/ returns only intentional historical refs.

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Audit reference: ARCP SDK Audit v1.1 (2026-05-19)

[luisllaver]

"Hi @agentruntimecontrolprotocol/php-sdk, I noticed that your README, composer.json, and CHANGELOG still reference v1.0 of the protocol. To align with the current state of the protocol, I suggest updating the links in README.md to point to the latest draft specification (spec/docs/draft-arcp-02.1.md), updating the description in composer.json to v1.1, and either updating or contextualizing the version reference in CHANGELOG.md. You can verify the changes by running grep -rEn 'v1\.0|draft-arcp-02' in your repository. For more information on the current protocol, please refer to the AURA Open Protocol documentation at https://dev.auraopenprotocol.org."