[BenGardiner]

Summary

Support Python 3.11 across packaging, diagnostics, and CI

Closes #562

Changes

• Lower the supported Python runtime floor from 3.12 to 3.11 for the project package metadata.
• Add Python 3.11 as an explicitly supported classifier and keep older Python versions rejected.
• Constrain incompatible dependency versions and regenerate the lockfile to ensure clean installs on Python 3.11.
• Update canarchy doctor to accept Python 3.11 while still rejecting unsupported older versions.
• Expand CI to test Python 3.11, 3.12, and 3.13 on Linux.
• Add a clean packaging smoke test for Python 3.11 covering version reporting, doctor checks, scaffold capture, and DBC decode.
• Update related documentation, contributor guidance, launch/command docs, and release notes.
• Preserve Python 3.12 requirements for optional openpilot integration.

see BenGardiner#1 and the session there for more details

Test plan

• uv run python -m unittest discover -s tests -v
• uv run ruff check
• Manual run against a representative fixture or live interface

Documentation

• CHANGELOG.md updated under [Unreleased]
• docs/command_spec.md updated (if the command surface changed)
• docs/event-schema.md updated (if the structured-output shape changed)
• Touched docs/design/ spec updated (EARS syntax)
• Touched docs/tests/ spec updated (Gherkin Given/When/Then)
• AGENTS.md / docs/agents.md updated (if agent workflows changed)
• mkdocs.yml nav updated (if any new docs pages were added)

Safety

• Active-transmit commands require --ack-active
• SECURITY.md reviewed against the new behaviour