docs: prepare v0.1.0 release documentation

[CoderDeltaLAN]

Summary:

• Move documented changes under a v0.1.0 changelog heading.
• Clarify pre-release security reporting boundaries.
• Add packaging and tag/release verification requirements to release docs.

Scope:

• Documentation only.
• No code changes.
• No tag.
• No GitHub Release.

Validation:

• ./scripts/check.sh passed.
• git diff --check passed.
• Packaging smoke passed for sdist and wheel from temporary environments.
• Pre-push fsck passed.

Risk:

• Low; release documentation wording only.

Rollback:

• Revert this PR if the release documentation needs to return to the previous pre-release wording.