docs(#341): document agent content migration to fullsend-ai/agents

[fullsend-ai-coder]

Add AGENTS.md section noting that agent definitions, skills, and harness configs have moved to fullsend-ai/agents. Add deprecation README.md in each stale scaffold directory (agents/, skills/, harness/) to prevent contributors from modifying the wrong copies.

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Closes #341

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[github-actions]

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[fullsend-ai-review]

🤖 Finished Review · ✅ Success · Started 3:11 PM UTC · Completed 3:18 PM UTC
Commit: b776cf6 · View workflow run →

[fullsend-ai-review]

Review — PR #500

Verdict: Approve

Clean, well-scoped documentation change that implements exactly what issue #341 requested: an AGENTS.md section documenting the agent content migration to fullsend-ai/agents, plus deprecation READMEs in the three stale scaffold directories.

Checks performed

Dimension	Result
Correctness	✅ All three scaffold directories (agents/, skills/, harness/) exist at the stated paths. Deprecation READMEs are placed correctly. Paths in AGENTS.md are accurate.
Security	✅ No secrets, no injection patterns, no Unicode steganography, no permission changes. PR body is clean.
Intent & coherence	✅ Change precisely matches issue #341's proposed fix — no scope creep. Section placement in AGENTS.md is logical (after existing scaffold sync rules, before Go development guidance).
Style & conventions	✅ Heading level, link format, path formatting, and imperative tone all match existing AGENTS.md conventions.
Docs currency	⚠ See follow-up note below.
Cross-repo contracts	⏭ Skipped — no exported interfaces modified.

Follow-up: stale references to deprecated paths

Multiple documentation files still reference the deprecated scaffold paths as authoritative sources. This is pre-existing staleness (not introduced by this PR), but the new AGENTS.md guidance creates a mild contradiction with these references:

• docs/agents/README.md and all agent doc files (code.md, fix.md, prioritize.md, retro.md, review.md, triage.md) link to scaffold harness YAMLs as canonical sources
• docs/guides/user/customizing-agents.md references raw GitHub URLs pointing to the scaffold harness
• docs/guides/user/running-agents-locally.md contains examples using the deprecated scaffold paths

Additionally, the Go scaffold package (internal/scaffold/scaffold.go) still embeds and serves content from these directories at runtime via //go:embed, so the files remain operationally necessary until the code is migrated. The AGENTS.md wording ("will be removed" — future tense) is accurate but contributors should be aware the files cannot be deleted yet.

These are separate follow-up items, not blockers for this PR.

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Protected paths detected — this PR modifies files under one or more
protected paths. The review agent cannot approve PRs that touch these paths.
A human reviewer must approve this PR.

Protected files in this PR:

• AGENTS.md

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Labels: PR adds documentation about agent content migration — the documentation label applies