hotfix: align repository documentation with v0.4.1

[manavanandani]

Summary

• align repository, SDK, quickstart, and CI installation guidance with v0.4.1
• add the missing v0.4.0 release history and document the v0.4.1 documentation patch
• separate Streamable HTTP server and client commands into executable two-terminal steps

Why

v0.4.0 shipped with stricter conformance validation, async lifecycle support, and configurable RPC timeouts, but several primary repository documents still directed users to v0.3.1. Because a hotfix: merge publishes the next patch version, the installation guidance targets the resulting v0.4.1 release instead of becoming stale immediately after merge.

Developer impact

Users receive consistent package pins across the repository and published package documentation, an accurate release history, and HTTP examples that can be followed without blocking the client command. This change does not alter runtime behavior, schemas, or the protocol draft version.

Validation

• strict MkDocs build passed
• Ruff checks passed
• SDK suite passed: 15 tests
• runtime suite passed: 55 tests
• SDK and runtime source distributions and wheels built successfully
• released v0.4.0 packages were installed from PyPI and their framework extras were verified
• flagship evaluation passed: 8/8 checks
• async evaluation passed: 3/3 checks
• rendered documentation and stale-version audits passed

Release

The hotfix: title triggers the existing patch-release automation, which advances package metadata and the runtime package README from v0.4.0 to v0.4.1 after merge. spec/protocol.md remains at 0.3.1-draft; this documentation hotfix does not change the protocol version.