Add CODE_OF_CONDUCT.md (Contributor Covenant 2.1)

[dean0x]

Context

Part of the v0.1.0 release-prep (PR #37, Phase C — community health). Every other
community-health file was added automatically (SECURITY.md, CONTRIBUTING.md,
issue/PR templates, dependabot), but CODE_OF_CONDUCT.md needs to be added
manually.

Why this is a manual step

The automated tooling consistently truncated when generating the standard
Contributor Covenant text inline (the file reproduces a verbatim enumeration of
prohibited harassing conduct, which appears to trip an output filter). Rather than
ship a half-written or paraphrased CoC, we're tracking it here for a manual drop-in
of the canonical file.

How to add it

curl -o CODE_OF_CONDUCT.md \
  https://raw.githubusercontent.com/EthicalSource/contributor_covenant/release/content/version/2/1/code_of_conduct.md

Or copy from https://www.contributor-covenant.org/version/2/1/code_of_conduct/

Then:

1. Replace the enforcement contact placeholder ([INSERT CONTACT METHOD]) with the
   maintainer's contact (e.g. deanshrn@gmail.com, already public in git history).
2. Confirm CONTRIBUTING.md already links to it (it does — "Code of Conduct" section).
3. Commit on the release branch: docs: add Contributor Covenant 2.1 code of conduct.

Acceptance

• CODE_OF_CONDUCT.md present at repo root (Contributor Covenant 2.1)
• Enforcement contact filled in
• Linked from CONTRIBUTING.md (already done)

[dean0x]

Moving from v0.2.0 to v0.4.0 — RELEASING.md lists CODE_OF_CONDUCT.md as an unmet one-time release prerequisite: "Add CODE_OF_CONDUCT.md (tracked in #38) if not already present". Pulling it forward to v0.4.0 to keep the release runbook accurate.