[lesnik512]

Closes #323.

Adds a Versioning section to AGENTS.md and removes the "public rename ships a silent alias" rule from Code style. Since #350 and #351, renamed names and config fields warn, so the old rule and its OpentelemetryConfig example no longer matched the code.

The section records four rules:

• what counts as breaking;
• breaking changes ship only in a major, except dropping an end-of-life Python, which ships in a minor as 1.11.0 did and as Drop Python 3.11 once it reaches end of life, and with it core's typing-extensions dependency #272 plans for 3.11;
• a rename warns with DeprecationWarning for at least one minor and is deleted in the next major, with pointers to deprecated_module_getattr and BaseConfig._renamed_fields;
• breaking changes get a "Breaking changes" section in the release notes.

One deviation from the issue text: the issue lists "raised floors" as breaking without qualification. Floors have been corrected in patch releases (#259, #300, #328) because the old floor never worked. The rule treats only raising a floor that the code ran correctly with as breaking, and calls a correction a fix.

Verified: just adr-check passes, and lychee in the CI job's offline mode reports no broken links in AGENTS.md.