cds get: missing CHANGELOG entry for breaking default-behavior change (#493)

[RonaldHensbergen]

Summary

PR #493 changed cds get's default behavior in a way that's a meaningful
breaking change, but the PR's diff includes no CHANGELOG.md entry for it.

Previously, cds get with no --remote flag copied a profile from the
current local repository checkout (via the now-deleted
_find_project_root() helper). After #493, the no-flag default instead
downloads this project's upstream repository from GitHub at the main
branch (DEFAULT_REMOTE / DEFAULT_REF in cli/getter.py), requiring
network access and fetching upstream main rather than the user's local
(possibly uncommitted) working tree.

Existing users/CI that relied on the old default (e.g. testing local
profile changes before committing, or working offline) will silently start:

• making network calls to api.github.com where none were made before,
• fetching upstream main instead of their local checkout's current state,

with no deprecation warning. They now need to discover and pass
--local . to restore the previous behavior.

This is called out as an intentional design change in the PR description,
so it isn't a hidden bug -- but it should be documented in CHANGELOG.md
under a ### Changed (or ### Breaking) heading so it's visible in release
notes, consistent with how other behavior changes in this repo are tracked.

Proposed fix

Add a CHANGELOG.md entry under [Unreleased] describing:

• the new default download-from-GitHub behavior,
• that --local <dir> is the way to restore the previous local-checkout
  behavior,
• a reference to feat: download cds get profiles from GitHub instead of local checkout #493.

Context

Raised during review of #493.