docs: add AGENTS.md maintenance guidance

[kunchenguid]

Intent

Captain-authorized firstmate preamble rollout: ensure this public video-artifact/dotfiles repo's existing AGENTS.md carries the canonical firstmate '## Maintaining this file' self-governance section. SMALL additive doc change only - append the exact canonical four-line block at the end of AGENTS.md if missing; do not rewrite other content, do not touch other files, do not create AGENTS.md if absent. Idempotent if the section is already present. Public repo: keep the change minimal and additive; never commit .no-mistakes/ validation evidence.

What Changed

• Add a self-governance section to AGENTS.md that defines what project knowledge belongs there and how to maintain it concisely.

Risk Assessment

✅ Low: The change is a tightly scoped, additive AGENTS.md documentation update with no runtime or behavioral code impact.

Testing

Verified the target checkout and diff scope, then exercised the root agent-instructions surface with an exact-content check. The canonical section is present once at the end, prior guidance is unchanged, and AGENTS.md is the only changed file. This documentation-only agent-configuration change has no rendered UI, so the content-verification transcript is the reviewer-visible evidence.

Evidence: Canonical AGENTS.md rollout verification

PASS: AGENTS.md is the only changed path. PASS: The root agent guidance ends with one exact canonical "Maintaining this file" section. PASS: All preceding content is byte-for-byte the base revision, with only the required separator newline added before the appendix.

PASS: AGENTS.md is the only changed path.
PASS: The root agent guidance ends with one exact canonical "Maintaining this file" section.
PASS: All preceding content is byte-for-byte the base revision, with only the required separator newline added before the appendix.

Pipeline

Updates from git push no-mistakes

✅ **intent** - passed

✅ No issues found.

✅ **Rebase** - passed

✅ No issues found.

✅ **Review** - passed

✅ No issues found.

✅ **Test** - passed

✅ No issues found.

• Inspected git diff 20007ac07e65838ee4b2fc1ea5fa9abc6417a876 6ecf51c3824f89f11df5b515416e4102c60ac33c -- AGENTS.md and changed-path scope.
• Ran a Node-based end-to-end content verification against the checked-out target, asserting that AGENTS.md is the base content plus exactly one final canonical section and no other paths changed.

✅ **Document** - passed

✅ No issues found.

✅ **Lint** - passed

✅ No issues found.

✅ **Push** - passed

✅ No issues found.